Earth Science

• Geology is the systematic study of preserved records caused by natural processes.

The Solar System

• The Big Bang Theory posits that enormous quantities of matter formed and spread across space.
• Stars developed from local concentrations of mass collected by gravity, similar to the dust clouds that formed protoplanets.

Properties of Planets

• Planets orbit the sun.
• They possess sufficient mass to have gravitational force to form a sphere.
• Planets have dominant gravitational influence leading to the absence of smaller objects along their orbit.

Types of Planets

• Terrestrial planets include Mercury, Venus, Earth, and Mars.
• Terrestrial planets are nearest to the sun and composed of high-temperature materials like iron and nickel.
• Jovian planets include Jupiter, Saturn, Uranus, and Neptune.
• All elements in the original condensed gas make up Jovian planets.
• Water minerals are interlocked in their crystalline structures.

The Planet Earth

• Earth heated up by several processes, including impacts from colliding dust particles.
• Gravity-driven compression of Earth's interior triggered nuclear reactions.
• Intense heat melted various materials and minerals that make up the Earth.

Earth's Compositional Zones

• The core, located at the center, is heavier and has a high density.
• The core consists of iron, nickel, and some minor elements, has a liquid outer layer, and a solid inner layer.
• The mantle is lighter, with a lower density and floats, consisting of iron, magnesium, silicon (Si), and oxygen (O2).
• Peridotite, including olivine which is unstable at 400 km and pyroxene which is unstable at 700 km, comprise the mantle.
• The crust is more chemically diverse.

Earth's Subsystems

• Heating and differentiation led to the formation of the lithosphere, hydrosphere, and atmosphere
• Oceans originated from H2O found as water or gas in crystal structures.
• Minerals containing water or gas released these elements, which condensed to form oceans.
• The prehistoric atmosphere consisted of N2, CO2, NH4, and S, before the presence of O2.

Atmosphere

• The atmosphere is connected to the formation of O2 and started with cyanobacteria.

Vital Statistics of Earth

• The Earth is 150 million km away from the sun.
• The Earth is an oblate spheroid, attributed to its rotation along its axis.
• The poles are flattened, making the distance from the poles to the core of high density.
• The equator bulges.
• The highly dense core's gravity pull is influenced by density measured using a surveying instrument aided by a plumb bob.

Eratosthenes' Contribution

• In the 3rd century, Eratosthenes approximated the circumference of the Earth.
• The equatorial circumference is about 400k km.

Density

• Weight in Fort Knox is greater than in a cave because Fort Knox's density due to its gold content.

Types of Rocks

• Continental rocks, dating back 3.8 Bya, are less dense and composed of Si, P, and Na.
• Oceanic rock, approximately 150 Mya, is basalt composed of Si, Fe, and Mg.

Isostasy

• The Pratt hypothesis states that mountains and plains are blocks "floating" on a dense underlying layer, with densities inversely related.
• Both mountains have different densities, but the same weight and identical cross-section.
• Airy's Hypothesis posits that mountains have roots, so rocks have the same density but unequal thickness.
• Rocks float on a denser substratum, standing at unequal heights compensated for by a root of its material projecting downward into the "fluid layer."
• Ocean basins feature mountain ranges, such as the mid-Atlantic ridge in the oceanic ridge system.

P and S Waves

• P-waves struggle to pass through liquid or hot material.
• S-waves cannot pass through liquids.
• A late-arriving wave suggests a liquid or hot layer beneath.

Crust Properties

• The crust is 5-40 km thick.
• Granitic crust is 35-40 km thick.
• Basaltic crust is 5 km thick.

Mantle Properties

• The mantle is the thickest layer, comprising 80% of Earth's volume.
• The Mohorovicic (Moho) Discontinuity divides the crust and mantle.
• The upper mantle, up to 400 km, contains peridotite rock rich in Fe and Mg.
• The lower mantle spans from 700-2,885 km and comprises MgO, SiO2, and FeO.
• Silicates are unstable at 700 km.

Earth's Spheres

• The lithosphere includes the crust and the solid upper mantle.
• The asthenosphere lies below the lithosphere.
• The asthenosphere contains weak or hot rocks, resulting in a low-velocity zone where seismic waves slow down.
• The Gutenberg-Weichert Discontinuity marks the boundary between the mantle and core.

Plate Tectonics

• Plate tectonics unifies geology, incorporating continental drift and seafloor spreading.

Continental Drift

• Alfred Lothar Wegener proposed continental drift, suggesting that all continents were once a supercontinent called Pangaea.
• Pangaea later split into Gondwana and Laurasia.

Evidence for Continental Drift

• Fossils of flora and fauna found on different continents
• Matching rock formations and geologic structures
• Patterns of ancient climates

Seafloor Spreading

• Harry H. Hess proposed seafloor spreading, differentiating between "drifters" and "fixers."
• Fixers used "land bridges"

Evidence for Seafloor Spreading

• The ocean floor is young, approximately 150 Mya, while continents are older, about 3.8 Bya.
• This suggests the ocean floor is more recently formed than the continents.
• Old crust is destroyed in ocean trenches.
• Rift valleys exemplify continents moving apart, such as the Red Sea.

Paleomagnetism

• Rocks contain magnet record the Earth's magnetic field's direction rocks were formed.
• Basaltic rocks contain magnetite grains.
• Changes in magnetic polarity would alter direction, and differences in orientation cause stripe-like features on the ocean floor.

Convection Currents

• Convection currents power seafloor spreading.
• Seafloor spreading is characterized by high heat flows and volcanism along mid-oceanic ridges.
• Temperature differences in the mantle produce convection cells.
• Descending convection currents in subduction zones drive plate movement.
• Convection currents operate in asthenosphere under lithosphere.

Plate Boundaries

• Movement of plates defines plate boundaries, which are divergent, convergent, & transform

Divergent Plate Boundaries

• At divergent boundaries, plates spread apart.

Convergent Plate Boundaries

• At convergent boundaries, ophiolitic complexes, which are pieces of oceanic plates and upper mantle uplifted onto continental plates, form.

Rock Types in Ophiolites

• From base to top, ophiolites consist of peridotite, gabbro, and volcanic rocks.
• The denser plate descends in subduction.
• Subduction occurs from ocean to continent, as ocean plates are more dense.
• Transform boundaries involve sliding plates.

The Geologic Rock Cycle

• The transformation of rocks and minerals into different forms due to geologic processes
• There are two approaches to understanding the rock cycle: the Rock Cycle and uniformitarianism.
• Rock type formation depends on geological processes (magmatism, volcanism, sedimentation, metamorphism).

Rock Composition

• A rock is an aggregate of one or more minerals, composed of one or more minerals.

Rock Classification

• Rocks are classified based on their origin, as igneous, sedimentary, or metamorphic.

James Hutton

• James Hutton noted of the cyclic nature of geologic events.

• Hutton observations in Siccar Point, England led him to create principle of Uniformitarianism.

• "The present is the key to the past.”

• Laws of nature that now prevail have always prevailed.

• Rocks are formed by similar processes in the past.

Igneous Rocks

• Extrusive includes basalt, andesite, dacite, rhyolite
• Intrusive includes gabbro, diorite, granodiorite, granite

Sedimentary Rocks

• Biologic includes coal, chert, limestone
• Chemical includes dolostone, evaporites
• Clastic includes conglomerate, breccia, sandstone, siltstone, mudstone, shale

Metamorphic Rocks

• Non-foliated includes quartzite, marble
• Foliated includes slate, schist, gneiss

Geologic History

• The geologic time scale includes: Pre-Cambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary periods.

Catastrophism vs. Uniformitarianism

• Catastrophism, associated with Baron George Cuvier, explains geologic features as caused by catastrophic events, estimating Earth's age at 6,000 years.
• Uniformitarianism explains geologic features with slow, gradual processes.

Siccar Point Observations

• Sediments were deposited horizontally.
• Deformation occurred.
• Erosion formed an Unconformity.
• Sediments were deposited on top of the erosional surface.
• Uplifting occurred.

Steno's Laws of Deposition

• Nicholas Steno created stratification or bedding.
• Law of Superposition states rocks are disposed in horizontal layers, oldest at bottom and youngest at top.
• Law of Original Horizontality states sediments deposited in water would normally form horizontal layers.
• Law of Lateral Continuity states when sediments are deposited in water they spread laterally in all directions.
• Faunal Succession includes fossils of organisms which follow ascending order during geological events.
• Faunal Assemblage are all animal fossils in layer or "strata".
• Chronological arrangement of geologic events by comparing physical relationship of rocks and fossils
• Relative Dating Methods measure chronological arrangement of geologic events by physical relationship of rocks and fossils.
• Law of Inclusion states a rock included in another an older the one encompassing (xenoliths) and found in igneous.

Laws of Cross-Cutting Relationships

• Rock/structure intersecting another is younger than the one cut
• Faults, folds, and dikes

Unconformities

• Major interruptions in the geologic record
• Angular Unconformity, strata below unconformity are distributed by folding and tilted with respect to strata above
• Nonconformity, identified with layered sedimentary rocks/ layered above eroded igneous or metamorphic

Disconformity

• Older beds below are parallel to younger beds
• Absolute Dating(Radiometric), radioactivity, spontaneous decay of elements particles releasing energy
• Elements normally are unstable decay

###Types of Dating

• Alpha
• Beta
• Isotopes produced
• Electron lost
• Electron captured

###Geomorphology

• Study of landforms, their description, interpretation, and as well evolution

###Landforms

• Individual topographic features(cliff)
• Land Topography, Earth Surface Condition
• Relief; Manifest difference elevation

Structure

• Arrangement nature & orientation of materials
• Processes of Various actions combining to produce land forms and structures.

###Rock Hardness

• Resistance to scratching by another substance
• Controlled by atomic structure

###Mineral Properties

• Is the result of light/color the eyes identify, can change colors is a luster appearance.
• Minerals that can not change color
• Magnetite, galena, azurite, malachite, sulfur, changes color

###Chalcopyrite

• Is a chemical process of variety colors

###Streak of Minerals

• Is a color of powdered in mineral form of mineral

###Graphite

• Is a regular arrangement of atoms

###Crystal Habit

• Is an internal arrangement of the atoms and molecules
• Mineral's tendency is split into plain, it is a line of weakness
• Parallel to atomic plains angles of 60 to 120 degrees
• Fracture is a separation, mineral break, that are irregular and nonplanar
• Ratio of substance between volume between light (color), streak between habit,cleavage & specific gravity

###Oxides

• Magnetite, Sulfides= pyrite
• Sulates=Gypsum,Carbonates =Calcite& dolomite

###Phosphate

• Chlorine/Halides
• Feldspar/Silicates

###Compositional Variation

• Not expressed in simple formulas
• brought ionic susbtatutions that make solid solutions and lattices