Earth Science Summary Essentials PDF

EARTH SCIENCE SUMMARY TARBUCK | LUTGENS | TASA Patrick Sam M. Buenavista  I EARTH’S INTERNAL STRUCTURE EARLY EVOLUTION OF EARTH Materials sorted by Density / Composi...

EARTH SCIENCE SUMMARY TARBUCK | LUTGENS | TASA Patrick Sam M. Buenavista  I EARTH’S INTERNAL STRUCTURE EARLY EVOLUTION OF EARTH Materials sorted by Density / Compositional Differences, forming 3 layers: Crust, Mantle, and Core. Earth is also divided based on physical properties: Lithosphere, Big Bang at 13.7 BYA; large explosion that sent all matter flying Asthenosphere, Upper & Lower Mantle, Outer & Inner Core. outward. Its debris of entirely Hydrogen & Helium began to cool and condense into the first stars and galaxies. Nebular Theory propose that solar system bodies evolved from rotating cloud (Solar Nebula). Nuclear fusion converts hydrogen & helium into other elements. At 5 BYA, nebula contracted from gravitational interaction among particles, possibly triggered by supernova; it rotated faster until the inward pull of gravity and outward force from rotational motion of nebula is balanced, then assuming flat disk w/ proto-Sun in center. Gravitational energy is converted into heat that broke the dust grains into energetic atomic particles, & temperatures remain low at a distance; at low temp (-200oC), particles converted into thick layers of frozen water, CO2, NH4, & CH4 (some still remain in Oort Cloud). The contraction period and gravitational heating is ended by the Formation of the Sun. The decrease in temp caused substances to condense into tiny particles and coalesce. Iron, nickel, and rock-forming elements formed rocky metallic clumps, forming into Planetesimals, which later coalesced into Terrestrial Planets and meteorites. Because of high temp & weak gravitational fields, inner planets Crust is thin, rocky layer including Continental & Oceanic crust. were unable to accumulate lighter elements hydrogen & helium. Oceanic is 7km thick Basalt at 3g/cm 3 and 180MYO. And due to low temp, Jovian planets formed w/ high percentage. Continental is 35-70km Granodiorite and 2.7g/cm3 and 4BYO. Circumference of Earth is 40,066 km or 24,896 mi. Mantle is solid, rocky at 2890km depth, comprising 82% of Earth’s volume, and consisting of Peridotite (Mg-,Fe-rich). 1 Astronomical Unit is 150 million km; Sun-Earth distance. Because of increasing pressure, mantle gradually strengthens Mercury is 0.3, Venus is 0.7, Mars is 1.5 w/ depth. Jupiter is 5.2, Saturn is 9.5, Uranus is 19.2, Neptune is 30. Upper Mantle from crust-mantle boundary to 660km depth; divided into Lithosphere (crust & uppermost mantle, 100-250km) Hydrosphere is dynamic continuously moving mass of water. and Asthenosphere (weak w/ small melting, mechanically Most prominent feature is the Ocean w/ 71% of Earth surface at separated from lithosphere). 3,800km deep and 97% of Earth’s water. Lower Mantle is from 660km to 2890km, very hot and capable of gradual flow. Core is Fe-Ni alloy, at 11g/cm3 and 14g/cm3 in center, divided to Outer Core (liquid 2,260km thick / at 5150km depth; generated magnetic field) and Inner Core (1,216km radius, solid due to immense pressure). Continental Drift proposes continents move instead of being stationary. Plate Tectonics provided first comprehensive model of Earth’s internal workings; lithosphere is broken into plates, continuously moving at 5cm/yr, driven by unequal distribution of heat. It produces convergent, divergent, and transform plate boundaries. Continents are flat above sea level w/ ave elevation of 0.8km. Largest feature are Mountain Belts (thick sequences of uplifted squeezed highly deformed rocks in Circum-Pacific belt, Alps, Himalayas, Appalachians, and Ural) and Shields (expansive flat regions of crystalline rocks, covered w/ thin veneer sedimentary Atmosphere is envelope of air surrounding the Earth. rocks called Stable Platform that is nearly horizontal except if The energy exchange between atmosphere, surface, and space warped to form large basins or domes). produce the effects of Weather and Climate. Noctilucent Clouds are thin streaks of clouds in Troposphere at 80km altitude. 90% of the atmosphere is below 16km. The higher the altitude, the lesser the pressure. At surface, pressure is 1000 millibar. At Mt. Everest, it is 300 millibar. Biosphere includes all life on Earth. Geosphere is solid Earth beneath the atmosphere and ocean, extending from the surface to center of planet at 6380km deep; largest sphere. Soil is the thin veneer of material at surface that Ocean Basins are 3.8km below sea level, or 4.5km lower than supports plant growth. Its solid portion is mixture of weathered average elevation of continents. Continental Margins is portion rock debris and organic matter. of seafloor adjacent to major landmass, including shelf (extend seaward from shore; flooded extension of continents), the slope that are free to move throughout the entire metallic structure; (steep drop-off from shelf to floor of deep ocean; boundary of attraction between negative electrons and positive ions. continents and deep-ocean basins), and rise (gradual incline of Metals are malleable, ductile, and ductile. slope; thick accumulations of sediments that moved downslope) Ionic & Covalent solids are brittle and often fracture. Deep-Ocean Basins lie between continental margins & oceanic ridges. Part include Abyssal Plains (flat), Trenches (depressions Properties of Minerals 11,000km deep; narrow), and Seamounts (submerged volcanic structures, sometimes forming long narrow chains, and forming Optical large lava plateaus). Luster appearance/quality of light reflected at surface Ocean Ridges are the most prominent feature on ocean floor, Diaphaneity ability to transmit light. forming continuous belt w/ mountains from fractured & uplifted Color most conspicuous property yet misleading. igneous blocks. Streak color of mineral in powdered form; consistent Habit / Crystal Shape Common or characteristic shape of individual crystals or II aggregate of crystals. Include equant, bladed, fibrous, tabular, prismatic, platy, blocky, banded, granular, and botryoidal. MATTER AND MINERALS Mineral is any naturally occurring inorganic solid w/ orderly Mineral Strength crystalline structure and definite chemical composition. How minerals deform under stress is determined by Type and Strength of Bonds. Rock is any solid mass of mineral or mineral-like matter that Hardness measure of resistance to abrasion/scratching. occur naturally. May be an aggregate of mineral, or entirely of Most useful diagnostic property. one mineral. Some are composed of non-mineral matter (obsidian, pumice, coal). Cleavage tendency of mineral to break along planes of weak bonding, forming smooth flat surfaces. Atoms are smallest particles that can’t be chemically separated. Described by number of cleavage directions and Neutrons & Protons form the nucleus, surrounded by Electrons angles at which they meet. in a cloud form. Protons (+1) and Neutrons (/) are very dense w/ Tenacity mineral’s resistance to breaking, bending, cutting almost identical mass, while Electron (-1) have negligible mass or other forms of deformation. (1/2000 proton). Electrons move around in Principal Shell, each w/ energy level & specific number of electrons; outermost shell Fracture formed by minerals equally strong in all direction, contains Valence Electrons (interact to form chem bonds). either Irregular (uneven), Conchoidal (smooth), Splintery or Fibrous. Most atom, except hydrogen & helium, were created by nuclear fusion inside massive stars during supernova explosions. As the ejected material cooled, newly formed nucleus attract electrons to complete the atomic structure. Atomic Number (number of proton) determine chemical nature; all atoms w/ same # of protons have same chemical & physical properties. Elements w/ similar properties are grouped into Groups (column), each w/ corresponding number of valence: Specific Gravity Number representing ratio of mineral’s weight to the weight of equal volume of water; describe density of minerals. MINERAL GROUPS Rock-forming Minerals make up most rocks on Earth’s crust. Only 8 elements make up the RFM and represent 98% by weight of continental crust. O, Si, Al, Fe, Ca, Na, K, Mg. Noble gas (except helium) has very stable electron arrangement and tend to lack chemical reactivity. Silicate Minerals Octet Rule: atoms tend to gain, lose, or share electrons until Contain oxygen and silicon, and most (except quartz) w/ surrounded by 8 valence electrons. additional elements. All have the silica tetrahedron. Primary elements that join silicates are Fe, Mg, K, Na, & Ca. Chemical Bond is transfer or sharing of electrons that allow The most abundant are Feldspars (>50% of crust). each atom to attain full valence; for atoms w/ no 8 electrons on Quartz is 2nd-most abundant mineral on continental crust, and outermost shell. only common mineral made entirely of silicon & oxygen. Ionic Bond if valence are transferred, and form ions. Tend to cleave between silicon-oxygen structures rather than Covalent Bond if valence are shared between atoms. across them. Most crystallize from molten rock as it cools. Each Metallic bond if valence are shared among all atoms. silicate mineral has a structure and chemical composition that indicate the conditions under which it formed. In Ionic Bond, the atom that lose electron is Positive Ion. The atom that gains electron is Negative Ion. Light Silicate Minerals In Covalent Bond, atoms both share the atoms, forming a strong Most common are Feldspar, Quartz, Muscovite, & Clay mineral. attractive covalent force driven by positive protons and negative Light in color, w/ SG of 2.5, and w/ Al, K, Ca, Na. electrons. Feldspar is most abundant group, w/ two cleavage directions at In Metallic Bond, the bonding force results from each atom 90o, relatively hard (6), and physically differentiated by striations contributing its valence electrons to a common pool of electrons on Plagioclase (Ca/Na) that are absent in K-feldspar (K). Quartz is hard (7) w/ conchoidal fracture. Muscovite is member of Mica, w/ excellent 1-D cleavage, and relatively soft (2.5 – 3). Clay Minerals form as products of chemical weathering. Dark Silicate Minerals Contain Fe & Mg, and includes Pyroxene, Amphibole, Olivine, Biotite, and Garnet. Iron gives dark color & high SG (3.2 – 3.6). Olivine is major constituent in dark-colored igneous rocks, abundant in the mantle, black to olive green color, glassy, and forms small granular crystals. Pyroxenes are also important in dark igneous rocks. Augite is the most common member, black, opaque, w/ 2 directions of cleavage at nearly 90o angle. Amphibole is next, with Hornblende as the most common, dark green to black, w/ 2 cleavage directions at 60o & 120o angles, and make up the dark portion of light-colored rocks. Biotite is dark, Fe-rich mica w/ excellent 1-D cleavage, common in light-colored igneous rocks, and differ from other dark silicate by its shiny appearance. Garnet is glassy, no cleavage, conchoidal fracture, often brown to deep red. Hope Diamond is 45.52-carat gem cut from a larger 115-carat Non-Silicate Minerals stone discovered in India in mid-1600s. The original stone was Groups divided based on negatively-charged ions, resulting to cut to become part of crown jewels of France and in possession minerals w/ same structure, type of bonding, and physical prop. of King Louis XVI & Marie Antoinette. Stolen during the French Make up 8% of crust. Revolution in 1792. In 1800s, it became part of the collection of Henry Hope and is on display at the Smithsonian in DC. Some of the most common non-silicates belong to Carbonates, Sulfates, and Halides. Economic non-silicate belong to Sulfides, Oxides and Native Elements. Ore Deposit is naturally-occurring concentration of one or more metallic minerals that can be extracted economically. Also applied to some non-metallic minerals (Fluorite, Sulfur). A deposit may become economic depending on technological advancements and market demand.  III Vesicular common features of extrusive rocks having voids (vesicles) left ROCKS by gas bubbles that escape as lava solidifies. Often form in the upper zone of lava flow where cooling is rapid, or when ejected during explosive eruptions (Pumice). Glassy Molten rock is quenched and cools quickly to become solid during volcanic eruptions; results when unordered ions are “frozen in place” before they are able to unite an orderly crystalline structure. Pyroclastic / Fragmental From consolidation of individual rock fragments ejected during explosive volcanic eruptions. Ejected particles may be very fine ash, molten blobs, or large angular blocks. Common type of rock include Welded Tuff. Granite (Felsic) Coarse-grained igneous rock from large masses of magma that slowly solidify at depth. Uplifted during mountain building. Rhyolite is extrusive equivalent and composed of light-colored silicates w/ frequent glass fragments and voids, indicating rapid cooling in surface environment. Rhyolite deposits are less common and less voluminous. Obsidian is common natural glass w/ higher silica content similar to granite; dark color from small amount of metallic ions in clear glassy substance. Pumice forms when large amount of gas escape from molten rocks to generate a grey, frothy mass. Igneous Rocks Andesite (Intermediate) Magma or Lava that cools and crystallizes. Medium-gray, fine-grained volcanic rock, common w/ porphyritic Magma is molten rock generated in the mantle, buoyantly rising textures w/ phenocrysts of light rectangular plagioclase or black towards the surface. elongated amphibole. Diorite is intrusive equivalent, resembling granite but with no visible quartz crystals and higher percentage of dark silicates. Basalt (Mafic) Most common extrusive igneous rock, very dark green to black fine-grained composed of pyroxene, olivine, and plagioclase. Gabbro is intrusive equivalent. Bowen’s Reaction Series Arrangement of minerals crystallizing over specific temperature. As magma cools, certain minerals crystallize first at relatively high temperatures. Magmatic Differentiation As magma cools, minerals selectively remove certain elements from the magma, and leaves remaining melt depleted of these elements. This changes magma chemistry from parent magma, forming more secondary magmas. In Crystal Settling, earlier-formed minerals are denser than the melt and sink at bottom of magma chamber. When remaining Igneous Textures melt solidifies, the rock has different chemical composition. Fine-grained Igneous rock that form at surface or as small intrusive mases within upper crust where cooling is rapid. Crystals are so fine Sedimentary Rocks grained they are distinguished only by polarizing microscope. Sediments from weathering products eroded and transported by Commonly characterized as Light, Intermediate, or Dark in color erosional agents that are deposited and lithified by compaction and cementation. Coarse-grained “Sedimentary” indicates the nature of rocks; derived from Latin Form when large masses of magma slowly crystallize at great sedimentum meaning “Settling”, referring to solid material that depth, consisting of mass of intergrown crystals roughly equal in settled out from fluid. size and large enough to be identified w/o microscope. Detrital Sedimentary Rocks Formed from detritus (solid particles from weathered rocks), Porphyritic dominated by Clay minerals and Quartz (most abundant product When minerals crystallize in different environmental conditions, of chemical weathering of silicate minerals; extremely durable resulting to large crystals embedded in a matrix of smaller and very resistant to chemical weathering). crystals; large crystals are Phenocrysts, smaller is Groundmass. Detrital sed rocks are classified according to Particle Size, as it is convenient and give information of depositional environment.  Chemical & Biochemical Sedimentary Rocks Derived from ions carried in solution, which does not remain dissolved in water and precipitate out to form chemical sediment due to physical processes. Also derived from water-dwelling organisms to form shells and hard parts. Limestone is abundant sed rock composed of Calcite from bio- chemical sediments secreted by marine organisms and from seawater. Coquina is easily identified biochemical limestone; coarse rock of loosely cemented shell and shell fragments. Chalk is soft, porous rock of microscopic calcareous planktons (forams, cocolithophores). Travertine is inorganic limestone formed when chemical changes or high-water temp increasing CaCO3 content that it precipitates. Groundwater is the source of travertine deposited in caves. Dissolved silica precipitates to form varieties of microcrystalline quartz, including Chert (light color), Flint (dark), Jasper (red), and Agate (banded). Rock Salt and Rock Gypsum precipitate from evaporation. Gypsum is basic ingredient of Plaster of Paris. Coal is sed rock mostly of organic matter (plant structure that are chemically altered but identifiable); end-product of burial of the large amount of plant material over extended period of time. Ideal deposition environment is a Swamp (anoxic). Over time, overlying weight compresses the deeper seds, reducing pore space and volume. Strata or Beds is single most characteristic feature of sed rocks Separated by bedding planes (flat surface along w/c rock tend to separate or break; marks new episode of sedimentation). Fossils are most important inclusions in sed rocks. When gravel-sized particles predominate, it is Conglomerate if rounded & Breccia if angular (not transported far from source). When sand-sized particles predominate, it is Sandstone. Shale is most common sed rock made of very fine-grained seds of clay minerals. The stronger the current, the larger the particles carried. Gravels are moved swiftly by river, rockslide, & glaciers. Sands are moved w/ less energy; common in wind-blown dune, Metamorphic Rocks river deposits, & beaches. Formed from preexisting rocks (parent rock) altered by increase Silt & Clay settle very slowly and associated w/ quiet waters. in temperature and/or pressure (but not melting). Compaction is most effective for very fine-grained sediments, Metamorphism is the process that changes the mineralogy, mostly by calcite, silica, and iron oxide. Identification is made by texture, and chemical composition of parent rocks. It occurs fizzing, hardest sed rocks, and orange/red color, respectively. when magma intrudes rock (Contact or Thermal Metamorphism) Cementation is most effective for sand & coarse sediments. or during mountain-building (Regional Metamorphism). Agents of Metamorphism are: underground. Reservoir Rock is porous & permeable rock that Heat – intruded by magma, or increase w/ depth yield petroleum & natural gas in sufficient qualities. Cap Rock is Confining pressure – increase w/ depth; more compact; an impermeable rock that stop the upward migration of oil & gas equal compression of rock in all directions escaping to the surface. Differential stress – compression in 1 direction: shortened in Hydraulic Fracturing or Fracking is process used in shale to direction of great stress, elongated in direction perpendicular create cracks in which fluids can flow by pumping liquids into to that stress; mineral grains flatten and elongate (ductile). the rock at very high pressure. Chemically active fluids – ion-rich fluids of water & volatiles, changing the arrangement & shape of grains, and changing the composition; minerals recrystallize and grow longer in direction perpendicular to compressional stress. Metamorphic Textures Degree of metamorphism is related in rock texture & mineralogy Low-grade Met forms denser & more compact rock. High-grade Met allow recrystallization and growth of larger crystals. Foliated Any nearly flat arrangement of mineral grains or structural features within a rock. Fundamental characteristic of Regional Metamorphism, driven by compressional stress and causing mineral grains to have parallel alignment. Examples are parallel alignment of platy minerals, flattened pebbles, compositional banding (dark & light minerals separate), and rock cleavage (split into tabular slabs). Slate is very fine-grained foliated rock composed of mica flakes, has excellent rock cleavage, generated from low-met of shale or when volcanic ash is metamorphosed. Black Slate has organic matter, Red Slate from iron oxide, and Green Slate has chlorite. Phyllite comprise muscovite & chlorite, larger than slate but not readily identifiable; degree between slate and schist. Has glossy sheen and wavy surface compared to slate. Schist are moderately-strongly foliated rocks from regional metamorphism, platy and readily split into thin flakes or slabs. Many originate from shale, but term describe texture regardless of composition i.e. schist of biotite/muscovite is Mica Schist. Gneiss is banded met rocks predominated by elongate and granular minerals. Common minerals are quartz, feldspar, w/ lesser muscovite, biotite, and hornblende. Non-foliated Met rocks w/ no alignment, developed where deformation is minimal and parent rock is composed of minerals w/ simple chemical composition. Marble is coarse, crystalline rock from limestone, composed of interlocking recrystallized calcite crystals. Quartzite is very hard metamorphic rock from quartz sandstone on moderate- to high-grade metamorphism (quartz grain fuse). MINERAL RESOURCES Metallic Some important metal accumulations are produced by igneous and metamorphic processes. Magmatic Differentiation is important for basaltic magma where Chromite, Magnetite, and Platinum is generated; Layered UM Intrusions. Pegmatites results from crystallization in fluid-rich envi that enhances ion migration resulting to large crystals; granitic composition consisting of quartz, feldspar, muscovite, and gems of beryl, topaz, tourmaline. Hydrothermal Deposits originate from hot, metal-rich fluids associated w/ cooling magma bodies that move along fractures, cools, and precipitate metallic ions to form vein deposits. Disseminated Deposits are ores that are distributed is minute masses throughout the entire rock mass instead of being concentration in veins. Non-metallic Either as Building Materials, or Industrial Minerals. Includes Limestone, Aggregates, Gypsum, Clay, and Cement. Fossil Fuels Include Coal, Oil and Natural Gas. Oil Trap is geologic envi that allow for economically significant amount of oil/gas accumulate  Chemical Weathering changes the chemical composition of rock, decomposing into substance stable at surface condition. Water is the most important agent. Most effective in regions or warm temp & abundant moisture. Differential Weathering results from variations in the rate of weathering. Oxidation – iron contained in rocks will oxidize in the presence of oxygen (air) or water, forming yellow or red- brown rust on the surface. Carbonic Acid (H2CO3) – CO2 dissolved in water, which ionizes to form the reactive H+ ion and Bicarbonate ion (HCO3). This readily decompose rocks and form products that are water soluble; responsible for limestone caverns. The most abundant product of chemical breakdown of Feldspar is residual Clay Mineral. Weathering of K-felds is residual clay, a soluble salt (K bicarbonate), and silica (forms nodules or chert, or silica shells in ocean). Quartz is very resistant to chemical weathering. Chemical breakdown of silicate minerals yield Na, Ca, K, MG ions; form soluble products removed by groundwater, the iron combines w/ oxygen to form red-brown oy yellow soil, and Al, Si, O is joined w/ water to form residual clays Goldschmidt Stability Series (opposite order of Bowen’s) states that Olivine is least resistant, and Quartz is highly resistant to weathering. IV Soil Combination of mineral, organic matter, water, and air (at 45%, WEATHERING, SOIL, MASS WASTING 5%, 25%, 25%, resp.); portion of regolith supporting plant (External Processes) growth; accumulation of weathered debris. Regolith is layer of rock and mineral fragments formed by Weathering weathering. Soil Water is complex solution of many soluble Physical breakdown (disintegration) and chemical alteration nutrients, giving moisture for chemical reactions and nutrients. (decomposition) of rocks at or near Earth’s surface. Weathering attacks edges from 2 sides and corners from 3 sides, which Soil Texture is proportions of different particle size. Texture decompose faster than single flat surface. influences the soil’s ability to transmit water & air. Mechanical Weathering by physical forces that break the rock into smaller pieces without a change in composition. Frost Wedging – the frozen water in cracks enlarge the cracks, eventually producing angular fragments. The ice grows larger due to addition of water migrating from unfrozen areas, producing a Frost Heave. Salt Crystal Growth – evaporating water from breaking waves of salty groundwater penetrating cracks and pore spaces in the rock deposits salt crystals, growing larger and weaken the rock by pushing apart the surrounding grains. Common in rocky shorelines and arid regions. Unloading or Sheeting – large rock mass is exposed to erosion; concentric slabs begin to break loose due to the reduction of pressure when the overlying rock is eroded. The process generating the slab is Sheeting, and the process where the rock is eroded is Unloading. This form Exfoliation Domes. Bioturbation – activity of organisms like plants, burrowing animals, and humans. Spheroidal Weathering – weathering attacks corners and edges of angular fragments to form spherical shape. Soil particle usually form clumps w/ gives soil a particular structure called Peds. It can be Platy, Prismatic, Blocky, or Spheroidal. Soil Structure influence susceptibility to erosion and affects porosity & permeability. Prismatic & Blocky Peds allow moderate water infiltration, and Platy & Spheroidal by slower infiltration rates. Residual Soils from bedrock parent material. Transported Soils from loose sediments parent material. Controls of Soil Formation include Parent Material, Time, Climate, Organisms, and Topography. Parent Material is the source of weathered mineral mater that form soils. The Type of parent material affect rate of weathering and rate of soil formation, and its Chemical chemistry affect the soil’s fertility. The longer the soil is forming, the thicker it becomes and lesser it resembles the parent material (more time mean higher degree of weathering and rock decomposition). Variation in Temperature & Precipitation determine whether physical or chemical weathering predominates; also influence the rate and depth of weathering. Precipitation affect the degree to which various materials are leached from the soil, affecting fertility. Soil fertility depends on amount of organic matter present. The decay of organism forms various organic acid which hasten weathering process. Organic matter also aid water retention. Variation in topography produce varying localized soil types. Steep slopes poorly develop soils w/ insufficient water for plant growth, while Boglands form thick & dark soil rich in organic matter. The optimum terrain is Flat to Undulating Upland Surface, w/ good drainage, minimum erosion, and sufficient infiltration. Slope Orientation is direction a slope is facing, and the difference in amount of received solar radiation results to differences in temperature & moisture and influence nature of vegetation and soil character. Soil Profile Vertical section through all the soil horizons. Soil Horizon is the zones dividing the soil due to variation in composition, texture, structure, and color. O Horizon – organic material. Upper portion is plant litter, lower is humus. Has microorganisms. A Horizon – mineral matter, w/ humus & high biological activity. O-A horizon is called Topsoil. Soil Erosion Sheet Erosion – soil moved by thin sheets of water. E Horizon – light-colored w/ little Rills – tiny channels formed by moving current of water. organic mat. Zone of Eluviation and Leaching, removing finer Gullies – deeper cuts as rills are enlarged. particles and soluble inorganic Steeper soil enable faster water runoff and greater erosion; components by percolating water. leave steep slopes undisturbed. Grassed waterways prevent the formation of gullies and trap the soil washed by water. B Horizon – Subsoil. Zone of Erosion Accumulation. Enhances water Physical removal of material by water, wind, or ice. retention. May form very compact impermeable layer or Hardpan C Horizon – partially altered Mass Wasting parent material. Transfer of rock & soil downslope due to gravity; does not need water, wind, or glacial ice. The step following after weathering. Solum or True Soil is the O,A,E,B Combined effects of mass wasting and running water forms Horizons. Stream Valleys; narrow valleys if by water alone. Gravity is controlling factor of mass wasting, and several other A well-developed soil profile indicate a stable environmental factors take part in overcoming inertia and create downslope condition over extended time span, and the soil is Mature. movement: saturation with water, oversteepened slope, removal Immature Soil lack soil horizons, and soil formed on short time; of anchoring vegetation, and ground vibrations. characteristic of steep soils. Mass wasting is triggered when heavy rain saturate surface material, allowing gravity to set it in motion. When water fills Soil Taxonomy the pores, cohesion among particle is destroyed; saturation System for classifying soils on physical & chemical properties of reduces internal resistance of materials. Water also adds soil profile, and organize based on observable characteristics. weight to the mass of material.  Oversteepening triggers movement of unconsolidated Solifluction granular materials. Also form unstable slope and mass Occurs when soil is saturated w/ water and soggy mass flows movement in cohesive soil, regolith, or bedrock. Loose downslope at few mm/cm per day or year, common wherever granular particles assume a stable slope called Angle of water cannot escape from saturated surface layer by infiltrating Repose (steepest angle at which material remain stable. to deeper levels. Common in regions underlain by Permafrost. 25o to 40o; larger more angular particle maintain steepest slopes). Mass Wasting processes are defined by Type of Material, the Kind of Motion, and Velocity of movement. If Soil & Regolith dominate, terms are Debris, Mud, and Earth If Bedrock dominate, term is Rock. Type of Motion Fall – free falling of detached individual piece of any size, common steep slope, from freeze-thaw cycles, and bioturbation. Primary way which talus slopes are formed and maintained. Slide – material remain fairly coherent and moves along well-defined surface. Flow – material moves downslope as viscous fluid, saturated with water, and move as lobes or tongues. Rate of Movement Avalanche – very fast movement at high velocities resulting V when air is trapped and compressed beneath the falling mass of debris, allowing it to move as buoyant flexible RUNNING WATER & GROUNDWATER sheet across the surface. Creep – very slow particle movement at mm/yr or cm/yr. Rapid Forms of Mass Wasting Slump Downward sliding of mass of rock or unconsolidated material moving as a unit along a curved surface. Commonly forms thick accumulations of cohesive materials (clay). As movement occur, crescent-shaped scarp (cliff) is formed at the head, and block’s upper surface is tilted backward. Occurs because a slope is oversteepened. Rockslide When blocks break loose and slide down a slope. Occurs where rocks are inclined or when joints/fractures is parallel to slope. Hydrologic Cycle is unending circulation of water driven by Sun. Most common in spring when heavy rain & melting snow occurs. Debris Slide if material is mostly soil & regolith. Evaporation – process by which water turns to vapor, and how water enters the atmosphere. Transported by Debris Flow / Mudflow wind and form clouds that eventually precipitate. Relatively rapid type involving the flow of soil & regolith w/ large Infiltration – portion of water soaking into the ground, amount of water. Frequently follow canyons & stream channels slowly moving downward & seeping into lakes, stream, in semi-arid mountain. Debris Flow is a flowing tongue of well- or directly into ocean. mixed mud, soil, rock, & water. The rate of flow depend on slope Runoff – surplus water flows over the surface into lake and water content. Mudflow if material is fine-grained. and streams when Rate of Rainfall exceeds the Rate Lahar if volcanic material, occurring when highly unstable layers of ash & debris is saturated w/ water and flow down steep slope, of Absorption. often triggered by heavy rain. Transpiration – water absorbed by plant, then released into the atmosphere. Earthflow Materials rich in clay & silt w/ small amount of sand & coarse particles saturated by soil & regolith, often in hillsides in humid areas during heavy precipitation, leaving a scar on & slope and forms a tongue- or teardrop-shape mass that move downslope. Generally viscous, so it moves slower than Debris Flow; faster during wet periods. Also commonly occur with large slumps. Liquefaction occurs as porous clay- to sand-sized sediment is saturated w/ water, and losing cohesion during earthquakes. Slow Forms of Mass Wasting Creep Gradual downhill movement of soil & regolith, from the alternate expansion-contraction of surface material by freeze-thaw or wet- dry, lifting particle at right angle to slope. Aided by anything that disturbs the soil and when saturated w/ water. Water Balance is the volume that passes through each part of Ability of stream to erode & transport material is directly related the cycle annually. Over 1-year period, 380,000km3 of water is to flow velocity. Factors include: cycled, enough to cover the Earth surface by 1m. Gradient – slope of stream channel expressed as vertical 36,000km3 water that annually travels from land to water is the drop over specified distance. The steeper the gradient, the single most important sculpting agent on Earth’s land surface. more energy available for streamflow. Water that runoff instead of infiltrating depends on: (1) intensity Channel Shape, Size, Roughness – affect amount of friction; and duration of rainfall, (2) amount of water already in the soil, larger channel have more efficient flow because smaller (3) nature of surface material, (4) slope of the land, and the (5) proportion of water is in contact with the channel. Smooth type and extent of vegetation. channel promotes a more uniform flow; irregular channel filled w/ boulders create turbulence to slow the stream. Runoff is dominant if surface material is highly impermeable or Channel Size increases downstream as more tributaries give is saturated. Runoff initially flows in broad, thin sheets which more volume of water. eventually form rills and gullies. Drainage Basin Discharge – volume of water flowing past a certain point in a Land area that contribute water to a river system. given unit of time, in m3/s or ft3/s, determined by multiplying Divide is imaginary line separating the drainage basin of one a stream’s cross-sectional area by its velocity. Streamflow is stream from another. Continental Divide separates continents highest in wet season. Discharge increase toward the mouth into large drainage basins. as well as flow velocity. Mississippi River has largest drainage basin in North America. Intermittent Streams only flow in wet periods. Ephemeral Streams only flow occasionally after heavy rainstorm River Systems Involve network of stream channels and entire drainage basin. Longitudinal Profile is cross-sectional view of stream from its Divided into: source area (headwater) to its mouth. Sediment Production Zone – located in headwater region of river system where most of the sediment is derived. A stream’s ability to accumulate and transport soil & weathered Sediment Transport Zone – region where the sediments are rock is aided by raindrops. When ground is saturated, rainwater transported through channel network along Trunk Streams. cannot infiltrate so it flows downslope and transport materials. When balanced, the amount of sediment eroded from banks Once flow if confined in channel, the erosional power of stream equals the amount deposited elsewhere in the channel. is related to slope and discharge. The stream’s ability to erode Sediment Deposition Zone – region where river slows as it bedrock is enhanced by the particles it carries. reaches the ocean or another large water body, reducing the energy of transported sediment and either accumulate as delta or moved offshore by ocean currents. Drainage Pattern Nature of drainage pattern varies depending on Kind of Rock in which stream developed and/or Structural Pattern of faults/folds. Dendritic Pattern is the most common, irregularly branching tributary streams forming where underlying material is uniform, which erosion doesn’t control pattern of streamflow but rather controlled by direction of slope. Radial Pattern when streams diverge from central area typically on isolated volcanic cones and domal uplift. Rectangular Pattern exhibit right-angle bends when bedrock is crisscrossed by series of joints/faults which guides the direction of valleys. Trellis Pattern is rectangular pattern in which tributaries are parallel to each other, in areas Streams transport all sizes of weathered rock material, as well underlain by alternating band of resistant & least-resistant rocks. as sort them; finer particles are carried more easily than coarse. Sediment Load is transported by stream by: Dissolved Load – brought to stream by groundwater and dispersed throughout the flow. The velocity of streamflow has no effect on the stream’s ability to carry dissolved load. Precipitation occurs when chemistry of water changes, when organism create hard parts, or when water enter inland ‘sea’ in arid climate w/ high evaporation rate. Suspended Load – most streams carry the largest part of load in suspension, creating the muddy appearance which indicates the specific gravity of particles that also influences settling velocity. Flat grains sink more slowly than spherical, and dense grains fall to the bottom more rapidly than less dense. The slower the Settling Velocity and higher the Flow Velocity, the longer the sediment stays suspended and farther the distance it is carried. Streamflow Bed Load – material too large to be carried in suspension, Water may flow in 2 ways: moving along the bottom, and is important for erosion by Laminar Flow – in straight-line paths parallel to stream downcutting stream. Particles move by rolling, sliding, and channel, common in slow-moving streams. saltation (jump or skip), depending on their shape. Turbulent Flow – erratic characterized as swirling motion, Movement is less rapid and more localized. contributing ability to erode. Important factor is water’s flow velocity; increase velocity, more turbulent. Strength of current Capacity is maximum load that is transported per unit of time. increases in deeper parts of channel; friction is greatest in the Greater discharge means greater stream capacity. Large rivers banks and bed of stream channel. with high flow velocities have large capacities. Competence is measure of stream’s ability to transport particle Depositional Landforms based on size. Faster streams have greater competency regardless of channel size, and increases proportional to the Delta forms where sediment-charged stream enters still waters square of its velocity; if velocity doubles, the force of water is of lake, inland sea, or ocean. As stream motion slow, sediments increased 4x, as boulders are transported during exceptional are deposited, and as delta grows outward the stream gradient floods because of increased incompetence. lessens, eventually causing channel to be choked w/ sediments deposited and forming Distributaries. Deposition occurs when stream slows, reducing competence; when flow velocity is less than settling velocity. Sorting occurs Natural Levees are formed by successive floods over many as various sizes are separated in stream transport. years parallel to the channel. When stream overflows, velocity Sediments deposited by streams are called Alluvium. slows and deposits coarse sediment in strips bordering channel Streamflow differs from Sheet flow as it is confined in a channel. while fine sediment is deposited over valley floor forming very gentle slope of natural levees. The area behind levees is poorly Bedrock Channels are streams actively cutting into solid rock, drained, forming Back Swamps. Tributaries that cannot enter a typically form in the headwater where steep is slope and forming river because of bocking levees will flow parallel to the river and potholes. Channel pattern is controlled by underlying geologic called Yazoo Tributaries. structure, exhibiting winding or irregular patterns. Alluvial Fans develop where high-gradient stream leaving a Alluvial Channels are streams with bed & banks composed of narrow valley in mountainous terrain and comes out suddenly unconsolidated sediments or alluvium. Channel pattern changes into broad flat plain or valley floor, forming due to abrupt drop in in shape because sediments are continually eroded, transported gradient and the change from narrow to a less-confined channel and redeposited, depending on the average size of sediments, at the base, causing the stream to drop load quickly in distinct channel gradient, and discharge. It reflects the stream’s ability cone- or fan-shaped accumulation. Coarse material is dropped to transport at unform rate w/ the least energy; the size & type of near the apex of the fan, while finer material is carried to base. sediment determine the nature of stream channel. Meandering Streams – streams that transport suspended Flash Floods forms a rapid rise in water levels depending on loads in bends. Streams flow in deep, smooth channel and rainfall intensity & duration, topography, and surface conditions. transport mud (silt, clay), sand, and fine gravel. They evolve Artificial Levees are earthen mounds built on river banks to over time as individual meanders migrate across floodplain. increase volume of water the cannel can hold. Most commonly Erosion occurs at outer bend where turbulence & velocity is used stream-containment structures. They have steeper slopes greatest; Cut Bank. Debris from cut bank are deposited in than natural levees. Point Bars in inside bends. Meanders migrate laterally, and Flood-controlled Dams are built to store floodwater and let it bends also migrate down valley as erosion is more effective slowly out, lowering the flood crest by spreading over longer downstream side of meander. Cutoff is new, shorter channel time span. Not effective as sedimentation lowers the volume of segment formed when the meander upstream erode material water and delta/floodplains downstream erode as it is no longer between two meander through narrow neck of land between replenished. them; abandoned bend is called Oxbow Lake. Channelization involves altering stream channel to speed the Braided Stream – stream of complex network of converging flow of water to prevent reaching flood height, either by clearing & diverging channels threading among island or gravel bars channel or dredging to make it wider & deeper. Artificial Cutoff giving an interwoven appearance, and forming where large straightens the channel by shortening the stream, increasing proportion of load is coarse material and stream has highly flow velocity and gradient. Larger discharge w/ flooding can be variable discharge; they are wide and shallow. dispersed more rapidly. Stream Valley consists of channel and surrounding terrain including the valley bottom (lower, flatter area partially or totally Groundwater occupied by stream channel, and the sloping valley walls that Represents the largest freshwater reservoir readily available. rose above the valley bottom. Stream valley are formed by the It is important as erosional agent as it dissolves rock and allow streamflow, weathering, overland flow, and mass wasting. formation of sinkhole & subterranean cavern; also an equalizer of streamflow; water in river is from groundwater. It is sourced Base Level is the lowest elevation to which a stream can erode from water infiltrating through pores, with amount depending on its channel; level at which mouth enters ocean, lake, or another slope steepness, nature of surface material, intensity of rainfall, stream, accounting that stream profiles have low gradients near and type & amount of vegetation. the mouth. Sea Level is the Ultimate Baselevel while Temporary or Local Baselevel include lakes, resistant rock layers, and main Belt of Soil Moisture is surface film on soil particles in near- streams that acts as baselevel for tributaries. Any change in surface zones with voids that enhance infiltration. baselevel cause readjustment of stream activities. Zone of Saturation is zone where all open spaces in sediment & rock is completely filled w/ water; water here is Groundwater. Steep gradient & channel above baselevel results Downcutting Unsaturated Zone is area above water table where soil & rock as dominant activity. Abrasion & hydraulic power of fast-moving is not saturated w/ water; this can’t be pumped by wells as the water slowly lower the stream bed, resulting to V-shaped valley water clings too tightly to soil. w/ steep sides. Most prominent features are Rapids and Water- falls. Significant increase in gradient is caused by variation in Water Table separate Saturated & Unsaturated Zones. Usually erodibility of bedrock into which channel is cutting. subdued replica of surface w/ highest elevation beneath hills Rapids are formed by resistant beds acting as temporary base- and decrease toward valleys, and at surface in wetlands. level upstream while allowing downcutting to continue down- Irregular surface due to variation in rainfall and permeability, stream. Waterfalls where stream makes abrupt vertical drop. and because groundwater moves very slowly; water piles up in Once stream has cut the channel closer to baselevel, erosion is high areas between stream valleys, which subsides during times less dominant, takes meandering pattern and results to valley of ceasing rainfall and approach the level of adjacent valleys, widening. Continues lateral erosion is caused by shifting of the but is often prevented when new supply of rainwater is added. stream’s meanders produces broader, flat valley floor covered w/ alluvium called Floodplain. Incised Meanders are meandering channels that flow in steep, Factors influencing Groundwater Storage & Movement: The nature of subsurface material influences rate of movement narrow valleys, either caused by dropped sea level or uplift. and amount of groundwater that can be stored. Porosity is percentage of pore spaces over total volume of rock which affects the quantity of water stored. Pore spaces depends on size & shape of grains, how they are packed, the degree of sorting, and amount of cementing materials. The smaller the pore spaces, the slower the groundwater moves. Permeability is ability of material to transmit fluids. If spaces in between grains are too small, water cannot move i.e. the clay has high porosity, but is impermeable. Aquitards are impermeable layer that prevent water movement. Aquifers are permeable rock strata that transmit groundwater. Groundwater moves by gravity from areas where water table is high to zone where water table is low. Water moves in looping curves throughout saturation zones as a compromise between pull of gravity and tendency to move areas of reduced pressure. Environmental Problems Land subsidence also occur when water is pumped faster than natural recharge process can replace it, particularly in areas underlain by thick layers of loose sediments. Groundwater can be contaminated by sewage or saltwater. Bacteria may be mechanically purified if aquifer is composed of sand or permeable sandstone. Geologic Forms by Groundwater: Caverns are created at or below water table in saturation zone; acidic groundwater follows lines of weaknesses in the rock, dissolving and creating cavities which enlarges into caverns. Calcium carbonate is deposited by dripping water, forming Travertine or Dripstones. Groundwater goes to surface by: Deposition of dripstone is not possible until caverns are above Springs is where water flows freely from the ground, sourced the water table in unsaturated zone, commonly occurring as from water in zone of saturation from precipitation; result when streams cut the valley deeper and lowering the water table as water table intersects ground surface. Many form when aquitard elevation of river drops. Stalactites hang in the ceiling, first blocks the downward movement of groundwater and forces it to depositing around the edge of water drop, continuously forming move laterally. Another when permeable bed (aquifer) outcrops a hollow limestone tube where water moves through, remains in a valley. Perched Water Table is localized zone of saturation suspended, and falls to cavern floor; this is called Soda Straw. formed when aquitard is above the water table and water then Stalagmites is suppled from ceiling, which prevents formation accumulates. of hollow tube. Stalagmite-Stalactite joins to form Column. Hot Springs occur when groundwater circulates at great depth, is heated, and rapidly rises to the surface. Water is 6oC – 9oC Karst Topography are terrains shaped by dissolving power of warmer than average annual air temperature where it occur. groundwater. Karst regions lack surface drainage (streams). Geysers are intermittent fountain in which columns of hot water Occur rapidly in tropical climate due to abundant rainfall and & steam ejected w/ great force, rising 30m – 60m into the air, greater CO2 availability. Arid & Semi-arid areas do not develop occurring where extensive underground chambers exist within Karst due to inefficient groundwater; only occur if it is remnant. hot igneous rock. At the chamber’s bottom, water is under great Sinkholes are depressions in karst topography, formed either pressure due to overlying weight of water, preventing it to boil at when limestone below soil is dissolved by downward-seeping normal 100oC i.e. 300m-deep chamber will boil water at 230oC. rainwater w/ CO2 resulting to shallow depressions w/ gentle Heating causes water to expand & forces to surface, reducing slopes, or when cavern roof collapses under its own weight w/ pressure and lowering boiling point, which causes the water steep sides and great depth. deep w/in chamber turning to steam and cause geyser eruption. Tower Karst is maze of isolated steep-sided hills that abruptly Wells is hole bored into zone of saturation, serving as small rise from the ground, forming in wet tropical & subtropical region reservoirs into which groundwater migrates and pumped into w/ thick beds of highly jointed limestone. surface. Drawdown is effect when water table around the well is lowered when substantial amount of water is withdrawn, and decreases w/ increasing distance from the well, resulting into a Cone of Depression. VI Artesian Systems refers to situation when groundwater rises in a well above the level where it was previously encountered, GLACIERS, DESERTS, WIND occurring when (1) water is confined to aquifer inclined w/ one end exposed at surface and receive water, and (2) aquitards Glacier is thick ice mass originating on land from accumulation, above & below aquifer present to prevent water from escaping, compaction, and recrystallization of snow. forming a Confined Aquifer because overlying pressure forces Valley (Alpine) Glaciers are glaciers moving along down-valley water to rise. Greater distance from recharge area, the greater from accumulation center in its head; longer than their width. the friction and smaller the rise of water. Ice Sheets are enormous masses that flow out in all directions Nonflowing Artesian Well occurs when pressure surface is from one or more accumulation centers. below ground level. Ice Shelf are large, flat masses flowing into adjacent ocean, Flowing Artesian occurs when pressure is above the ground, floating, and extending seaward from coast but remain attached and well is drilled into aquifer. to land; thickest on landward side and thinner seaward. Artesian Springs occur when groundwater reach surface by Sustained by ice from adjacent ice sheet, from snowfall, and rising along natural fracture than artificially-produced hole. from freezing of seawater at the base. Ross and Ronne-Filchner Ice Shelves are the largest. Ice Caps are mass of glacial ice covering uplands and plateaus. Glaciers carry the largest blocks of all erosional agents, by: Piedmont Glaciers occupy broad lowlands at base of steep Plucking as it lifts and incorporates blocks loosened by moving mountain; form when valley glacier emerge from confining walls. glacier over fractured surface, and occurs when meltwater Outlet Glaciers are tongues of valley glaciers extending from penetrates and freezes along the cracks. the margins of larger ice masses and flows down-valleys. Abrasion as moving ice acts like sandpaper and polish surface below, producing Rock Flour making meltwater streams milky Ice moves in 2 ways: Plastic Flow within the ice, and as Brittle and long scratches and grooves called Glacial Striations Solid on the surface. Ice first behave as brittle until the pressure is equal to 50m. Plastic Flow occurs when pressure is >50m, The differential erosion by glaciers is controlled by: because of ice’s molecular structure; bond between layers of Rate of glacial movement weaker than those within, so when stress exceed bond strength Thickness of ice the layers remain intact and slide over another. Also ice moves Shape, abundance, and hardness of rock fragments within when entire mass slips along the ground, which happens in the the ice at the base of glaciers lowest portions. Erodibility of surface beneath the glacier Landforms created by Glaciers: Zone of Fracture is the uppermost 50m of glacier consisting of brittle ice, carried along piggyback-style by the ice below. Crevasses occur when glacier moves over irregular terrains and is subjected to tension, forming cracks. First experiment from glacial ice is conducted in Rhone Glacier of Switzerland in 19th century. Glacial Trough is U-shaped valley widened & broadened from being narrow valleys by glaciers, as well as straightening it. Trunk Glacier is the valley containing the main glacier. Hanging Valleys are valleys left standing above main glacial trough formed as trunk valley is eroded deeper than tributary streams that feed it. Cirques are bowl-shaped depressions w/ precipitous walls on 3 sides but opened on down-valley side, located at the head of glacial valley and characteristic w/ alpine glaciers as its zone of accumulation. Tarn is a lake at the cirque. Aretes are sinuous, sharp-edged ridge, while Horns are sharp, Ice Cap Climate is the climate classification of Antarctica which pyramid-like peaks projecting above surrounding, both forming average temperature of warmest month is 0oC or below. due to enlargement of cirques by plucking and frost action; aretes when cirques are in opposite sides of divide or as the Snow is the raw material from which glacial ice originates; ridge separated by two glaciers occupying parallel valleys, and glaciers form in areas where more snow falls than melt. horns as several cirques around single high mountain or Isolated Horns when cirques enlarge and converge. Zone of Accumulation is where snow accumulates & ice forms Fjords are deep, steep-sided inlet of the sea, forming as glacial with outer limits defined by the Snowline. Above the snowline, troughs submerge when glaciers retreats, and sea levels rises. snow thickens the glacier and promote movement. Zone of Wastage is below the snowline, with net loss of glacier as snow melt. Glacier also waste during Calving as large piece of ice breaks in front of glaciers, and create Icebergs. Calving is Glacial Deposits the primary means by which ice shelves lose mass. Glacial Drift is an ‘umbrella term’ for sediments of glacial origin regardless of how, where, or in what form it is deposited, divided Glacial Budget is balance or lack of between accumulation and into 2 distinct type: loss. If accumulation exceeds wastage, glacial front advances. if Till are unsorted materials directly deposited by glacier wastage exceeds accumulation, glacial front retreats. If balance, Stratified Drift are sorted sediments by glacial meltwater. the glacial front remains stationary. But the ice continues to flow Accumulation of stratified drifts consists of sand & gravel. forward; in retreat, ice still flows but not rapidly enough to offset wastage. Glaciers are sensitive to Temperature & Precipitation, Glacial Erratic are boulders in till different from bedrock derived providing clues to changes in climate. from source outside the area; may use to trace path of ice lobe. Moraines are layers / ridges of till and most widespread feature Variation in Earth Orbit – variation in incoming solar radiation of glaciers. is principal factor controlling Climate, proposed by Serbian Lateral Moraines are ridge of material sourced from the valley scientist Milutin Milankovitch. These cause little or no effect sides left when glacier melts. in total solar energy reaching the ground, but because they Medial Moraines are single dark stripe of debris formed when change the degree of contrast between the seasons; milder 2 valley glaciers converge to form a single stream. winter in mid-high latitudes means greater snowfall totals, End Moraines is ridge of till forming at glacial terminus, and is and cooler summers bring reduction in snowmelt. characteristics of ice sheets and valley glaciers, deposited as Major variation in climate is closely associated with changes accumulation equals wastage; the longer the front remains in geometry of Earth’s orbit, closely w/ periods of obliquity, stable, the larger the till becomes. causing the succession of Quaternary Ice Ages. Ground Moraines are rolling layer of till deposited as the ice o Eccentricity – variation of shape of Earth’s orbit front recedes, in between retreating ice front and End Moraine; o Obliquity – changes in angle of axis with plane of orbit has a levelling effect deranging existing drainage or poorly o Precession – wobbling of axis drained swampy lands if till is fresh. Terminal Moraines is the very first end moraine to form and marks the farthest advance of the glacier Recessional End Moraines are end moraines forming as the ice front occasionally stabilizes during retreats. Both are alike, except their relative positions. Broad, ramp-like accumulation of stratified drift is built adjacent to downstream edge of End Moraines and formed as suspended materials are dropped by meltwater. If associated w/ ice sheet, it is Outwash Plain; confined to mountain valley, its Valley Train. Kettles are basins/depressions formed when blocks of stagnant ice is buried by drift and eventually melt. Most are 2km diameter and >10m deep, often filled with water. Drumlins are streamlined asymmetrical hills of till, ranging from 15-60m height and 0.4-0.8km length. The steep side faces the direction from which ice advanced, and gentler slope in direction the ice moved. Commonly occur as Drumlin Fields. Streamlined shape indicating its molded in zone of flow w/in active glacier. Eskers are sinuous ridges of Sand & Gravel made from stream flowing in tunnels beneath the ice near the terminus of glacier. Kames are steep-sided hills of Sand & Gravel forming when meltwater washes sediment into openings and depressions in stagnant wasting terminus, eventually left when ice melts. Effects of Ice Age Glaciers Plate Tectonics explains the widely-spaced and non-periodic Glaciers also caused rivers to change flow directions. Presence onset of glacial conditions at various times, while Variations in of glaciers cause crustal subsidence and rebounds if it melts. Orbit explain the alternating glacial & interglacial episodes. Sea level changes when glaciers form or melts. During the Ice Other factors include Variations in chemical composition of the Age, ice left its imprint on almost 30% Earth land area. atmosphere (Ice Age atmosphere has less CO2 and CH4 – being Proglacial Lakes are water bodies beyond the outer limits of GHG) and Changes in Reflectivity of surface (ice covers reflect glacier or ice sheets, forming as meltwater is trapped. large portion of incoming solar energy back to space, decrease temp), and Changes in Ocean Currents (warm tropical currents Pluvial Lakes are formed when evaporation rates are lowered was weaker in Ice Ages). and precipitation is increased in areas beyond the margins of glacial environment, as a response to formation of glaciers. Most are now gone, with largest remnant being Great Salt Lake. Deserts Tillites are sed rock of lithified till, usually w/ striations and lie Dry region, either hot or cold, characterized by barren terrain atop grooved & polished rock surfaces or associated w/ sand- and low precipitation levels of 25cm/yr or 10in/yr, covering 42 stone & conglomerates deposited as stratified drift. million km or 30% of Earth’s surface. Dryness refers to situation 2 Precambrian glacial episodes were ID in 2BYA and 600MYA. in which water deficiency exists. Extensive glaciations may be caused by: Dry Climate is climate w/ yearly precipitation less than potential loss of water by evaporation. Within these regions, two climatic Plate Tectonics – areas w/ ancient glacial feature were once types are recognized: Desert/Arid and Steppe/Semi-arid as joined together (Pangea) and located in south latitudes. marginal, more humid variant representing transition zone that Movement is gradual so it cannot be used. surround desert and separates from bordering humid climates. Subtropical Highs are zones of high-pressure characterized by Depositional Landforms by Wind subsiding air current, coinciding dry regions in low latitudes and Wind deposits are (1) extensive blanket of silt called Loess, and resulting from prevailing global distribution of air pressure/wind. (2) mounds& ridges of sand from wind bedload called Dunes. Mid-latitude deserts/steppes exist because they are sheltered Loess are blanket of windblown silt, which tends to maintain by deep interiors of large landmass, far removed from ocean vertical cliff and lack any visible layers. Its worldwide distribution (ultimate source of moisture and precipitation) and presence of indicate sources from Deserts and glacial deposits of Stratified high mountains across paths of prevailing winds. Drift. Thickest & most extensive deposits in west & north China, sourced from desert basins in central Asia and give yellow color Geologic Processes in Arid Climates of Hwang Ho/Yellow River. Loess in US and Europe is sourced Produce the characteristic angular rock exposure, sheer canyon from glacial stratified drift. walls and rocky & pebble-/sand-covered surfaces. Weathered debris consist of unaltered rock & mineral fragments Sand Dunes are sand mounds or ridges common in deserts. As from mechanical weathering. Rock weathering is reduced due to moving air encounters and object, the wind sweeps around and lack of moisture. Chemical weathering forms clays & thin soils, over it and leaves a quieter wind shadows which saltating grains and rust-colored stain. deposit. With sufficient sand supply and wind blowing steadily Ephemeral Streams only carry water in specific episodes of enough, a dune forms. Many have asymmetrical shape w/ the rainfall. Flashflood occur because of sparse vegetation so runoff leeward (shadowed) slope as steep, and windward slope gently is unhindered and rapid. Other names are Wash/Arroyo (USA), inclined. Sand accumulates beyond the dune crest, and leeward Wadi (Arabia, N. Africa), Donga (S. America), Nullah (India). side (Slip Face) maintains 34o angle. Cross Bedding results as Streams lack extensive tributary systems in arid regions and layers formed inclined in the direction the wind is blowing, which water table is far below the surface. However, even running is preserved in rock record. water occurs infrequently, it does the most erosional process; most desert landform is formed by water. Wind mainly transport Factors influencing the Form & Size assumed by dunes include: and deposits sediments, forming dunes. Wind direction and velocity Sand availability Dry regions lack permanent streams and have Interior Drainage. Amount of vegetation present Alluvial Fans are sediments dropped by water moving down confined in canyons into gentler slopes at the base of mountain. Over time, fans coalesce to form Bajada (apron of sediment). During abundant rainfall, the basin floor turned into shallow Playa Lake before evaporation & infiltration removes the water. The dry, flat lake bed is called Playa, occasionally encrusted w/ salt (Salt Flats). Inselbergs are large bedrock knobs projecting above the basin from eroded mountain in late stages of erosion. Wind Erosion Moving air is turbulent, and its velocity increase w/ height above the surface. But its lower density compared to water gives it less capacity in transporting coarse materials and its not confined to Barchan Dunes are solitary crescent-shaped sand dunes with channels but spread over large areas. tips pointing downwind. Form where Sand supply is limited and Wind is an insignificant erosional agent, but more effective in surface is flat, hard, and lacks vegetation. They migrate slowly arid areas considering area’s dryness and scanty vegetation. at 15m/yr, with modest size (largest is 30m high, 300m wide). Deflation is the lifting and removal of loose material by wind. Transverse Dunes are series of long ridges separated by Because of low competence, it can only suspend fine particles troughs oriented at right angle to wind direction, forming in area like clay & silt. Larger grains are transported by Saltation; but w/ abundant sand supply, steady wind, and sparse/absent veg, particles larger than sand is not usually transported by wind. typical in coastal areas and common in arid areas where the Blowouts are shallow depressions and most noticeable result extensive wavy sand surface called Sand Sea. of deflation. Desert Pavement is the surface of coarse pebble & cobbles too Barchanoid Dunes is common dune intermediate between large to be moved by wind, forming as deflation lowers surface isolated barchans and transverse dunes, forming scalloped row by removing sand & silt from poorly sorted materials. oriented at right angles to wind direction and resembling series of barchans side-by-side. Longitudinal Dunes are long ridges of sand forming parallel to wind direction and moderate sand supply. Parabolic Dunes resemble Barchans, but the tip point upwind, forming where vegetation partially covers the sand along coasts. If vegetation is disturbed, deflation create blowout. Sand then is transported out of depression and deposited as a curved rim that grows higher as deflation enlarges blowout. Star Dunes are isolate hills of sand w/ complex form with 3-4 sharp-crested ridges diverging from central highpoint, forming where wind directions are variable. Wind erodes in part by Abrasion as windblown sand cuts and polishes exposed rock surface.  VII PLATE TECTONICS First theory to provide comprehensive view of the processes that produced Earth’s major surface features. Continental Drift developed by Alfred Wegener in 1915 and Global Ridge System is longest topographic feature on Earth suggests that continents joined together as Pangea. Evidence: surface, exceeding 70,000km long. Include Mid-Atlantic & Mid- fit along seaward edge of continental shelf on opposite sides Indian Ridges, and East Pacific Rise. Ridges are 2-3km high & of Atlantic Ocean by Sir Edward Bullard in 1960s. 1000-4000km wide. Along the crest is a Rift Valley indicating fossil of Mesosaurus, Lystrosaurus, and Glossopteris by tensional forces that pulls ocean crust apart at the ridge crest. Wegener Mechanism operating along oceanic ridges is called Seafloor rock successions and mountain belts of similar age Spreading, averaging 5cm/yr similar to human fingernails; Mid- late Paleozoic glacial period forming ice sheets in Southern Atlantic Ridge at 2cm/yr and East Pacific Rise at 15cm/yr. Hemisphere Elevated position of oceanic ridge is because new oceanic lithosphere is hot and less dense than cooler rocks away from Wegener’s theory was rejected due to credible mechanism; the ridge axis. It takes 80MY for new rocks to stabilize and stop gravitational forces of Sun-Moon forming the tides is not enough contracting. Thickness is age-dependent; older cooler rock, the to gradually move the continents. Harold Jeffrey stated that tidal greater the thickness: 80MYO rocks is about 100km thick. force strong enough would result to halting Earth’s rotation Continental Rift is elongated depression which widen to form a which didn’t happened. Wegener also suggested that continents narrow sea, occurring when divergent boundary develop within broke through thinner ocean crust like ice breaker, but there is continent. no evidence that ocean floor was weak to permit passage w/o being deformed. Wegener died in 1930 while returning from Eismitte in Greenland Ice Sheet. Convergent Boundaries Older denser portion of oceanic lithosphere descend into mantle Theory of Plate Tectonics is a far more encompassing theory at rates equal to seafloor production. Also called Subduction developed in 1968. Discoveries that led to this include a Global Zones. Subduction occurs because density of descending plate Oceanic Ridge System by US oceanographic research, from is greater than density of underlying asthenosphere; old oceanic earthquakes at great depths beneath deep-ocean trenches, and lithosphere is 2% more dense than asthenosphere. dredging ocean floors revealing oceanic crust at 180MYO and Deep-ocean Trenches are surface manifestation produced as with thin sediment accumulations. oceanic lithosphere descends into mantle. The angle of plate According to this model, the strong rigid Lithosphere floats atop subducting depends on age and density; young and buoyant weak plastic Asthenosphere, detached & moves independently. lithosphere descends at low angle. Most trenches in western Lithosphere is broken into lithospheric plates and in constant Pacific are deeper than eastern Pacific because they are very motion with respect to one another. dense and thickest slabs and descent at closer to 90o angle. Major Plate Minor Plate Ocean – Continental: buoyant continental block remains Pacific Caribbean floating while denser oceanic slab sinks. Reaching 100km North American Nazca depth, melting occurs w/in wedge of hot asthenosphere due South American Philippine to water contained in descending slab lowering melting point Eurasian Arabian in process of Partial Melting and generate molten material which rises and form Continental Volcanic Arcs. African Cocos Indo-Australian Scotia Ocean – Ocean: similar to ocean-continental collision, except that volcanoes rise from ocean floor and not from Antarctic Juan de Fuca continental platform, building an arc-shaped chain of *Minor plates are composed of oceanic lithosphere except Arabia. volcanic islands called Volcanic Island Arc or Island Arcs, generally located 100-300km from trenches. Example are Margin between plate include Divergent (constructive; resulting Aleutian, Tonga, Marianas, and Lesser Antilles (Atlantic mantle upwelling, form new seafloor), Convergent (destructive; seafloor beneath Caribbean). reabsorbed into mantle or form mountain belt), and Transform Continental – Continental: when one landmass moves (conservative; grind each other). toward margin of another landmass because of subduction of intervening seafloor, forming a mountain belt of deformed seds and met rocks w/ slivers of oceanic crust. Transform Boundaries Plates slide horizontally past one another without destroying or producing lithosphere, as discovered by J. Tuzo Wilson in 1965 who proposed that transform fault connect 2 spreading center. Most on ocean floor which offset segments of ridge systems, producing step-like margins, and part of linear breaks in seafloor called Fracture Zones. Active transform faults lie only between 2 offset ridge segments defined by weak, shallow earthquake; new seafloor a