Earth Science PDF

EARTH AS A UNIQUE PLANET Importance ✓ Weather forecasting – accurate predictions of the INTRODUCTION TO EARTH SCIENCE future wea...

EARTH AS A UNIQUE PLANET Importance ✓ Weather forecasting – accurate predictions of the INTRODUCTION TO EARTH SCIENCE future weather conditions ✓ Weather modification – to modify the weather such Earth Science is a field of study concerned with the planet as suppressing the hail and fog and weaken Earth or one or more of its parts. It includes the sciences used to hurricanes) – Dry Ice, Salt, and Potassium Iodide are study the lithosphere (the solid portion of the earth), the some of the compounds used in weather modification atmosphere (the gaseous surrounding of the earth), the (Cloud seeding). hydrosphere (the ice, water, and water vapor at or near the earth’s surface), the biosphere (the zone at or near the Earth’s surface that supports life) and space beyond the atmosphere. Earth Science covers a range of subject matter. It includes B. HYDROLOGIC SCIENCE AND ITS BRANCHES geology, geophysics, meteorology, climatology, oceanography, hydrology, astronomy, and astrophysics. - Study of the earth’s bodies of water - In its widest sense, hydrology encompasses the study BRIEF HISTORY OF EARTH SCIENCE of the occurrence, the movement, the physical, and chemical characteristics of water in all its forms within The origin of the Earth Sciences lies in the myths and legends of the earth’s hydrosphere. the distant past. The creation story which can be traced to a Babylonian epic of the 22nd century BC and which is told in the first chapter of Genesis proved to be the most influential. The story is cast in the form of Earth history and thus was readily accepted as an embodiment of scientific as well as of Engineering hydrology - concerned with the design of man- theological truth. made structures that control the flow and use of water. Earth scientist later made innumerable observations of natural Glaciology - the study of Glaciers and ice caps. phenomena and interpreted them in an increasingly multidisciplinary manner. The Earth Sciences, however, were Groundwater Hydrology - focuses on subsurface water in the slow to develop largely because the progress of science was unsaturated zones. constrained by whatever society would tolerate or support at any one time. Hydraulics - concerned with the dynamics and mechanics of water in its liquid state. THREE PRINCIPAL COMPONENT DISCIPLINES OF Hydrography - description and mapping of the bodies of EARTH SCIENCE water of the earth’s surface including the oceans with a particular concern on navigation charts. A. ATMOSPHERIC SCIENCE AND ITS BRANCHES Hydrology - the study of water on and within the ground. Aeronomy - study of the atmospheric regions above the lower Hydrometeorology - focuses on water in the lower boundary stratosphere. It deals with the phenomena such as airglow, of the atmosphere. auroras, and photochemical processes. Hydrometry - involves measurement of the surface water, Climatology - has something to do with the long term weather particularly precipitation and stream flows. conditions on a global scale. Limnology - the study of the lakes and inland seas. Meteorology - primarily concerned with the short-term weather variations in the atmosphere. Soil water physics - study of subsurface water in the unsaturated zones. Oceanography - the study of oceans and seas. Physical oceanography - the study of properties of sea water (waves, currents, tides) Chemical oceanography – study of composition of sea water Petrology - study of rocks and the physical, chemical, and biological processes that govern changes in composition of sea water in time and in Seismology - study of earthquakes space. Structural geology - study of the structures in the solid earth. Submarine geology - deals with the geologic evolution and topography of the ocean basins. Volcanology - study of volcanoes Biological Oceanography or Marine Biology - focuses on the Importance plant and animal life of the sea. ✓ Exploration for accumulations of fossil fuels (coal, oil, and natural gas, geothermal energy, and mineral deposits) Importance ✓ Earthquake prediction and control ✓ Selection of locations for buildings, roads, railroads, ✓ Development and management of water resources bridges, dams, and other major civil features. ✓ Concern for groundwater quantity and quality. ✓ Prevent drought and other climatic patterns. Characteristics of earth making it suitable for supporting life C. GEOLOGIC SCIENCE AND ITS BRANCHES Disciplines concerned with the physical chemical makeup of the solid earth. Our sun is a stable and long-lasting star Stars that are more massive than the sun burn hotter and Astrogeology - study of rock record on the moon, planets, and usually don’t live long enough for planets to develop life. Less their satellites. massive, younger stars are often unstable and are prone to blasting their planets with bursts of radiation. Economic geology - study of mineral commodities in which modern civilization is heavily dependent. Engineering geology - concerned with the engineering Water world properties of geologic materials, including their strength, It is unique among planets in our solar system for having water compactability, and permeability and the influence of these in its liquid form at the surface, in an amount conducive to life properties on the selection of locations for buildings, roads, evolving. Not too much to cover the mountains, and not so little and railroads, bridges, dams, and other major civil features. that it's a dry desert, as Mars and Venus. Geochemistry - the study of chemistry of rocks. Geochronology - study of the isotonic chemistry and age We’re at just the right distance from the sun dating rocks. Our planet receives enough energy to allow water to exist as a liquid on its surface. Too far, and the vital compound stays Geomorphology - study of landforms which is concerned with locked up as ice. Too close, and the water would rapidly the description of the features of the present terrestrial surface evaporate into the atmosphere. and an analysis of the process that gave rise to them. Geophysics - study of physical properties of rocks at the earth’s surface and interior. We have an ozone layer in the atmosphere to block harmful rays Mineralogy - study of minerals Ancient plantlike organisms in the oceans added oxygen to the atmosphere and created a high-altitude layer of ozone that Paleontology - study of fossils and fossil records. shielded species from lethal radiation. Pedology - study of soil Gas-giant neighbors ATMOSPHERE Jupiter. In general, gas giants tend to clump up near their home stars. But because they're toward the outside of our solar The atmosphere is the thin gaseous layer that system, their intense gravity conveniently catches wayward envelopes the planet. It is also where the weather and asteroids and comets. climate occurs. It is composed of gas layers that serves as protection Temperature from ultraviolet radiation and extraterrestrial objects Life seems to be limited to a temperature range of -15˚C to like asteroids. 115˚C. In this range, liquid water can still exist under certain The present atmosphere is composed of 78% conditions. Low temperature can cause the freezing of water, Nitrogen (N), 21% Oxygen (O2), 0.9% Argon (Ar), making liquid water unavailable while high temperatures cause and trace amount of other gases. the quick evaporation of water. One of the most important processes by which the heat on the Earth's surface is redistributed is through atmospheric circulation. There is also a constant exchange of heat and Energy moisture between the atmosphere and the The Earth has a steady input of either light or chemical energy, hydrosphere through the hydrologic cycle. cells can run the chemical reactions necessary for life. Too little sunlight or too few of the chemicals that provide energy to cells, such as iron or sulfur, organisms die. Light energy becomes a problem if it makes a planet too hot. Layers of the atmosphere Troposphere - is the layer of the atmosphere nearest to earth. All weather conditions happen in the troposphere. Four earth subsystems The Earth consists of four subsystems, across whose boundaries matter and energy flow. These subsystems include the Stratosphere - Most jets fly in this layer. The protective ozone lithosphere (the solid portion of the earth), the atmosphere is at the top of the atmosphere (It protects us from the (the gaseous surrounding of the earth), the hydrosphere (the ultraviolet radiation of the sun.) ice, water, and water vapor at or near the earth’s surface), and the biosphere (the zone at or near the earth’s surface that Mesosphere supports life). The mesosphere is the coldest layer of the These subsystems of the Earth interact with each other and atmosphere. these four subsystems are independent and have their Meteors burn up in this layer. respective mandates or functions. Each can only succeed if all Radio waves are reflected back to earth in the four subsystems are able to perform their respective functions. mesosphere. The Earth system is essentially a closed system. It receives energy from the sun and returns some of this energy to space. Thermosphere The thermosphere is the hottest layer of the LITHOSPHERE atmosphere. Curtains of light called auroras occur in this layer. The lithosphere is the solid part of the earth that includes the rocks of the crust and mantle, the metallic liquid outer core, and the solid metallic inner core. Exosphere Plate Tectonics plays an important role shaping the surface of the Earth. The exosphere is the outermost layer of the The primary driving mechanism is the Earth's internal atmosphere. Satellites orbit earth in the exosphere. heat, such as that in mantle convection. HYDROSPHERE To say that something is a mineral, it must have all the following characteristics: A dynamic mass of liquid that is in constant motion, evaporating from the surface and bodies of water to 1. It is naturally occurring (not man-made or machine the atmosphere, and will be back in the form of generated) precipitation, running in land, bodies of water, and 2. It is inorganic (not a byproduct of living things oceans again. 3. It has a definite arrangement of atoms, that is solid About 70% of the Earth is covered with liquid water with an orderly crystalline structure (hydrosphere) and much of it is in the form of ocean 4. Its chemical composition can be expressed in terms of water. chemical formula. Only 3% of Earth's water is fresh: two-thirds are in the form of ice, and the remaining one-third is present Water is not a mineral because it is not solid in structure. in streams, lakes, and groundwater. Despite the fact that pearl is naturally occurring, crystalline solid, and its composition can be expressed in a chemical formula, still it is not a mineral because it is organic, a byproduct of clams. Ice tube and iron nail are both man-made so they’re not considered as a mineral while graphite, The 5 major earth oceans snowflakes, salt, Gold, and Silver meets all the requirements to be called a mineral. ✓ ARCTIC OCEAN ✓ SOUTHERN OCEAN ✓ INDIAN OCEAN ✓ ATLANTIC OCEAN ✓ PACIFIC OCEAN Properties of minerals BIOSPHERE LUSTER The biosphere is the set of all life forms on Earth. It is the quality and intensity of reflected light It covers all ecosystems—from the soil to the exhibited by the mineral. rainforest, from mangroves to coral reefs, and from Can also be described as the general appearance of the plankton-rich ocean surface to the deep sea. the surface in reflected light For most of the life on Earth, the base of the food chain comprises photosynthetic organisms. During photosynthesis, CO2 is sequestered from the atmosphere, while oxygen is released as a by- Types of luster product. The biosphere is a CO2 sink, and therefore, an important part of the carbon cycle. Metallic - Minerals reflect light like metals. Metallic luster often tarnishes to a dull luster. (Example: ROCKS AND MINERALS MINERALS Galena Vitreous - The mineral reflects light like glass. In Chemistry, mineral is any naturally occurring chemical Sometimes glassy luster is used instead of vitreous. element or compound, but in mineralogy and geology, minerals (Example: Fluorite) are chemical elements or compound that have been formed Pearly - The luster of a pearl or mother of pearl. through inorganic processes. (Example is Biotite Mica) Silky - The luster of silk. It occurs in minerals with a fibrous structure. (Example: Satin Spar) Adamantine - The luster of a diamond Dull/earthy - The mineral does not reflect light and has the same appearance as soil. (Example: Limonite) HARDNESS CLEAVAGE AND FRACTURE is the measure of the resistance of a mineral to abrasion. Mohs Cleavage is the property of some minerals to break scale is used to determine the hardness of a mineral. along specific planes of weakness to form smooth, flat surfaces Mohs Hardness Scale is designed by German These planes exist because the bonding of atoms geologist/mineralogist, Friedrich Mohs in 1812. The test simply making up the mineral happens to be weak in those compares the resistance of a mineral relative to the 10 areas. reference minerals with known hardness. Some minerals do not break along cleavage planes but instead it is described as fracture, which is 10 Reference Minerals in the Mohs Scale irregular or without any definite pattern or direction. 1 – Talc 6 –Orthoclase Feldspar SPECIFIC GRAVITY 2 – Gypsum 7 – Quartz is the weight of the mineral compared to the weight of an 3 – Calcite 8 – Topaz equal volume of water. Native metals are the heaviest ones. 4 – Fluorite 9 – Corundum OTHER PROPERTIES 5 - Apatite 10- Diamond include magnetism, odor, taste, reaction to acid, fluorescence. Examples: COLOR ✓ Magnetite is strongly magnetic ✓ Sulfur has distinctive smell the color of a fresh surface mineral is a clue to their ✓ Halite is salty identification. A lot of minerals can exhibit same or similar ✓ Fluorite has the ability to disperse ultraviolet rays to colors. Individual minerals can also display a variety of colors visible light resulting from impurities and from some geologic processes like ✓ Calcite fizzes with acid as with dolomite but in weathering. powdered form. STREAK Mineral groups is the mineral’s color in powdered form. Silicates - minerals containing 2 of the most abundant obtained by rubbing a mineral on a white unglazed elements in the Earth’s crust, namely, silicon and tile or porcelain plate oxygen. Examples of streak: pyrite exhibits gold color but has Oxides - minerals containing Oxygen anion (O2) a black or dark gray streak. combined with one or more metal ions Sulfates - minerals containing Sulfur and Oxygen anion (SO4) combined with other ion Sulfides - minerals containing sulfur anion (S2) combined with one or more ions. Some sulfides are CRYSTAL FORM sources of economically important metals such as copper, lead and zinc. The form reflects the supposedly internal structure of the Carbonates - minerals containing the carbonate anion mineral. It is the natural shape of the mineral before the (CO3) combined with other elements development of any cleavage or fracture. Native Elements - minerals that form as individual elements. Metals and Inter-metals minerals with high thermal and electrical conductivity, typically with metallic luster, low hardness (gold, lead) Semi-metals - minerals that are more fragile than metals and have lower conductivity (arsenic, bismuth)  Nonmetals - nonconductive (sulfur, diamond) Igneous Rocks can also be classified as: Halides - minerals containing halogen elements combined with one or more elements Coarse-grained: takes longer to cool, giving mineral crystals more time to grow Fine-grained: cools quickly with little to no crystals ROCKS are naturally formed, non-living mass of organic and inorganic SEDIMENTARY ROCKS earth material consisting of one or more minerals that are held together in a firm, solid mass. are formed by the compaction and cementing together of sediments (materials that settle out of air and water), broken Rocks are classified by how they are formed, their pieces of rock-like gravel, sand, silt, or clay. composition, and texture Rocks change over time through the rock cycle No heat and pressure involve Strata layers of rock Types of rocks Stratification-the process in which sedimentary rocks are arranged in layers IGNEOUS ROCKS are rocks that form from the cooling of hot molten masses called magma (hot molten mass that can be found beneath the Two types of sedimentary rocks earth's surface) or lava (hot molten mass on the earth's surface). Clastic sedimentary rocks - Formed from broken bits and pieces of other existing rocks that settle out of water or air. Ex. Conglomerate, sandstone Magma can form Non-clastic sedimentary rocks ✓ When rock is heated ✓ When pressure is released Chemical - Formed from the materials that precipitated from ✓ When rock changes composition water. Ex: Gypsum, halite or salt. ✓ Magma freezes between 700 °C and 1,250 °C ✓ Magma is a mixture of many minerals Biological or organic - Formed from organic sediments that are remains of living organisms such as plants and shells. Ex. Two types of igneous rocks Limestone, coal Intrusive igneous rocks - Formed beneath the earth's surface. METAMORPHIC ROCKS Extrusive igneous rocks - Formed on the earth's surface. are formed when igneous or sedimentary rocks are subjected to heat and pressure. Examples of metamorphic rocks Igneous Rocks can also be classified as: Quartzite a coarse-grained metamorphic rock Felsic: light colored rocks that are rich in elements such as derived from sandstone. aluminum, potassium, silicon, and sodium Marble a metamorphic rock that comes from metamorphosed limestone or dolomite. Mafic: dark colored rocks that are rich in calcium, iron, and Slate formed when shale is subjected to heating magnesium, poor in silicon magma. Gneiss formed when conglomerate is exposed to heat and pressure ROCKS, MINERALS AND SOCIETY ORE MINERALS Earth's crust is the source of a wide variety of minerals, many of which are useful and essential to people. As a matter of How they are Found, Mined and Processed for Human Use fact, all manufactured product contains materials obtained from minerals. INTRODUCTION TO MINING Most people are familiar with the common uses of basic metals, is the process of mineral extraction from a rock seam including Aluminum in beverage can, Copper in electrical wires, or ore –a natural rock or sediment containing one or Gold in jewelry, and Silicon in computer chips. But fewer are more valuable minerals. The minerals can range from aware that pencil Lead does not contain Lead metal but is precious really made of the soft black mineral called graphite. Modern mining technology uses geophysical techniques that involve measuring the magnetic, The economic uses of rocks and minerals are important to us. gravity and sonic responses of rocks above and Consequently, a basic knowledge of the earth materials is around a prospective mineral ore body. essential to the understanding of all Earth science phenomena. is required to obtain any material that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. in a wider sense includes extraction of any non- Uses of some minerals renewable resource such as petroleum, natural gas, or even water. Feldspar used to make porcelain, enamel, and as a Mining of stones and metal has been a human activity building stone. since pre-historic times. Modern mining processes Mica used for insulation in electrical equipment, involve prospecting for ore bodies, analysis of the wallpaper, and fireproof materials profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land Talc used to make powder for cosmetic products after the mine is closed. Calcite used in manufacturing cement and mortar and for writing on the board Sulfur used in manufacturing sulfuric acid, explosives, SURFACE MINING dyes, insecticide, and soap Salt used as a preservative and additive is used to extract ore minerals near the surface of the earth. Borax used in manufacturing soap, enamels, glass, The soil and rocks that covered the ores are removed through washing powder, and welding blasting. Blasting is a controlled use of explosives and gas Apatite used for fertilizer graphite-used as pencil exposure to break rocks. lead Iron used in industry and infrastructure projects Aluminum used for roofing and in making planes, cars and other transport vehicles Three types of Surface Mining Mercury used in thermometers, barometers, and industries Titanium used in paint pigments and bulletproof since it was light but very strong OPEN-PIT MINING Gold used for coins, jewelry, and in coating other ornamental objects. Open-pit mining, also known as open-cast or open Silver used as conductor, making silverwares, coins, cut mining, is a surface mining technique of extracting and jewelry rock or minerals from the earth by their removal from Copper used in electrical wirings an open-air pit, sometimes known as a borrow. Diamond used in industry and in making jewelry Quartz used in making optical instruments, radio and This is the most common type of surface mining. Open electronic equipment because of its electrical pit means a big hole (or pit) in the ground. The pit in properties and in porcelain paints when in powdered mine is created by blasting with explosives and form drilling. It is used to mine gravel and sand and even rock. STRIP MINING Steps in Mineral Processing This mining type involves the removal of a thin strip of Sampling is the removal of a portion which represents overburden (earth or soil) above a desired deposit, a whole needed for the analysis of this material. dumping the removed overburden behind the deposit, Analysis is important to evaluate the valuable extracting the desired deposit, creating a second, component in an ore. This includes chemical, mineral parallel strip in the same manner, and depositing the and particle size analysis. waste materials from that second (new) strip onto the Comminution is the process where the valuable first strip. This mining method is used for coal, components of the ore are separated through crushing phosphates, clays, and tar mining. and grinding. This process begins by crushing the ores to a particular size and finishes it by grinding the ores "Strip mining" is the practice of mining a seam of into a powder form. mineral, by first removing a long strip of overlying soil Concentration involves the separation of the valuable and rock (the overburden); this activity is also minerals from the raw materials. referred to as "overburden removal". It is most commonly used to mine coal and lignite Dewatering uses the concentration to convert it to (brown coal). Strip mining is only practical when the usable minerals. This involves filtration and ore body to be excavated is relatively near the sedimentation of the suspension and drying of the surface. solid materials harvested from this suspension. FORMATION OF FOSSIL FUELS DREDGING INTRODUCTION TO FOSSIL FUEL This is the process of mining materials from the bottom of a body of water, including rivers, lakes, and oceans. are basically remains of plants and animals that died millions of years ago. They are the world’s primary Dredging is the removal of sediments and debris from energy source that provide most of the energy the bottom of lakes, rivers, harbors, and other water support in transportation, electricity, and industries. bodies. It is a routine necessity in waterways around They are natural and finite resources that are very the world because sedimentation—the natural process abundant and has a cheaper cost production of sand and silt washing downstream—gradually fills compared to other resources present on Earth. They channels and harbors. are considered as non-renewable energy source as they take millions of years to form. Coal, crude oil, and natural gas are all considered fossil fuels because they were formed from the fossilized, buried remains of plants and animals that UNDERGROUND MINING lived millions of years ago. Because of their origins, fossil fuels have a high carbon content. is used to extract the rocks, minerals and other precious stones that can be found beneath the earth’s surface. In underground mining, miners need to create a tunnel so they can reach the ore minerals. This kind of mining is more expensive and dangerous as compared to surface mining because miners Types of fossil fuels need to use explosive devices to remove the minerals from the rocks that cover them. COAL - It is an important and primary fossil fuel present on Earth. Coal resources are found predominantly where forest trees, plants and marshes existed before being buried and compressed millions of years ago. - Philippines uses approximately 50% coal resource to produce energy and electricity. There are four major ranks of coal. FORMATION OF FOSSIL FUELS 1. Anthracite is the highest rank of coal. It is a hard, - Millions of years ago the remains of prehistoric plants brittle, and black lustrous coal, often referred to as and animals are buried beneath the Earth’s surface. hard coal, containing a high percentage of fixed These remains were covered by mud. The mud carbon and a low percentage of volatile matter. sediment was buried by more sediments and It started 2. Bituminous Coal it usually has a high heating value to change into rock as the temperature and pressure and is the most common type of coal used in electricity increase. generation. It appears shiny and smooth at first - In that case fossil fuels are formed in a low oxygen glance, but when you look closely, you will see that it environment. The plant and animal remain were has layers. altered chemically by this process, and slowly 3. Subbituminous Coal is black in color and dull, and has changed into crude oil and natural gas. a higher heating value than lignite. - Through the spaces of permeable rock, the oils move 4. Lignite is also known as brown coal. It is the lowest upwards and will be trapped if it reached grade coal with the least concentration of carbon. impermeable rock. Oil companies can drill down through the impermeable rocks to get it out. - They are then able to turn it into products we can use, OIL such as petrol and diesel. On the other hand, coal can be extracted from the Earth through underground - Most of the oil that we are using today started mining. Once it has been extracted, it can be used to forming millions of years ago. Oil is an organic fuel power plants for electricity. material, mostly algae, which was buried in mud at the bottom of the sea and lakes. - It is used mainly to produce transportation fuels and petroleum-based products. Philippines imports crude DISADVANTAGES OF FOSSIL FUELS oil and petroleum from Saudi Arabia and Russia. Most of the market are Petron Corporation, Pilipinas Shell, LAND DEGRADATION and Chevron Philippines. - Petroleum products supply about 37 percent of U.S. - Unearthing, processing, and moving underground oil, energy needs, with the transportation sector gas, and coal deposits take an enormous toll on our consuming the most. landscapes and ecosystems. The fossil fuel industry leases vast stretches of land for infrastructure such as wells, pipelines, access roads, as well as facilities for NATURAL GAS processing, waste storage, and waste disposal. - In the case of strip mining, entire swaths of terrain— - It is a naturally occurring hydrocarbon gas with the including forests and whole mountaintops—are mixture of methane. It is the Earth’s cleanest fossil fuel scraped and blasted away to expose underground and is odorless and colorless in its natural state. coal or oil. Even after operations cease, the nutrient- - Natural gas is produced from sedimentary rock leached land will never return to what it once was. formation by forcing chemicals, water, and sand down - As a result, critical wildlife habitat—land crucial for a well under high pressure. The Philippines’ main breeding and migration—ends up fragmented and domestic source of energy is the Malampaya natural destroyed. Even animals able to leave can end up gas field which is located at Palawan Island. suffering, as they’re often forced into less-than-ideal habitat and must compete with existing wildlife for resources. WATER POLLUTION Coal, oil, and gas development pose myriad threats to our waterways and groundwater. Coal mining operations wash acid runoff into streams, rivers, and lakes and dump vast quantities of unwanted rock and soil into streams. Oil spills and leaks during extraction or transport can pollute drinking water sources and jeopardize entire freshwater or ocean ecosystems. EMISSIONS Types of Freshwater bodies - Fossil fuels emit harmful air pollutants long before ✓ Streams they’re burned. Indeed, some 12.6 million Americans ✓ Wetlands are exposed daily to toxic air pollution from active oil ✓ Lakes and gas wells and from transport and processing ✓ Rivers facilities. These include benzene (linked to childhood ✓ Hotsprings leukemia and blood disorders) and formaldehyde (a cancer-causing chemical). - A booming fracking industry will bring that pollution to more backyards, despite mounting evidence of the practice’s serious health impacts. Mining operations EARTH’S WATER RESOURCES are no better, especially for the miners themselves, generating toxic airborne particulate matter. Water has unique properties that allow it to move through almost anywhere on Earth. The water molecule found in your Strip mining—particularly in places such as Canada’s boreal glass of water today could have been buried with a fossil forest—can release giant carbon stores held naturally in the million years ago. In the prevailing billions of years, the wild. molecule possibly stayed solid in a glacier or liquid below the ground. The molecule surely was high up in the atmosphere and maybe inside the stomach of a dinosaur. Where will that water molecule go next? GLOBAL WARMING - When we burn oil, coal, and gas, we don’t just meet THE HYDROLOGIC CYCLE our energy needs—we drive the current global warming crisis as well. Fossil fuels produce large quantities of carbon dioxide when burned. Earth’s water exists in all three states and may be present in - Carbon emissions trap heat in the atmosphere and various environments. As it transforms from one state to lead to climate change. In the United States, the another, it must enter different processes. The process by which burning of fossil fuels, particularly for the power and water moves around on Earth’s surface is known as the transportation sectors, accounts for about three- hydrologic (water) cycle and is powered by the solar energy quarters of our carbon emissions. that comes from the sun. The water cycle consists of different processes. EARTH’S WATER RESOURCES Processes in the water cycle Water is the most critical nutrient necessary for sustaining life. Evaporation is a process of turning liquid into its If there is no water on earth, life would not exist and we would gaseous state. The gaseous state produced in this not have the kind of biodiversity that we have now. process is called water vapor. The water vapor evaporates from the surface water from oceans or freshwater ecosystems but only water molecules go to the atmosphere, the salt and other minerals stay in the reservoir. The energy from the sun causes this DISTRIBUTION OF EARTH’S WATER evaporation. The water resources of the Earth are made up of 97% salt Condensation is a process of turning gaseous water and 3% freshwater (Figure 1). This freshwater exists in molecule to liquid phase. The gaseous water molecule the solid-state as ice, polar ice caps, and glaciers and liquid stays in the atmosphere until it undergoes form in freshwater ecosystems and groundwater. Freshwater condensation to become tiny droplets of liquid. The ecosystems and groundwater serve as storage locations for droplets of liquids in clouds, which are blown about water and are known as reservoirs. the globe by the wind collide and grow, and fall from the sky as precipitation in the form of rain, hail, snow, These reservoirs comprise 3% of the fresh water available on etc. earth and include oceans, glaciers, groundwater, lakes, rivers, and the atmosphere. Water molecules present in reservoirs may pass through it very fast or may remain for a longer time.  Transpiration is a process wherein plants absorb MUNICIPAL AND COMMUNITY SOURCES water from the soil and release excess water vapor to the atmosphere through the pores of their leaves. - Households and businesses in a community may also Precipitation is a process wherein liquid or solid pollute the water supply. Activities such as the water molecules released from the clouds fall to the application of fertilizers and chemicals to lawns and ground. When liquid water reaches the ground, it farms cause water pollution. goes to rivers that stream down to oceans and lakes. - The chemicals and fertilizers dissolve in rainwater and On the other hand, water molecules that cascade as end up in nearby rivers or lakes. Also, underground snow stay longer on top of the mountains. This snow septic tanks develop leaks that may contaminate may stay as part of the ice in glaciers for hundreds or groundwater. thousands of years. - Besides, treated wastewater dumped by municipal Runoff plays an important part in the water cycle sewage treatment plants pollutes rivers or lakes wherein rainwater, melted snow and ice flow down because they are not be treated enough and still rivers and lakes. At the surface, the water may contain bacteria or hazardous chemicals. eventually evaporate and go back to the atmosphere. Even though water resources become polluted due to human activities, we need water for life itself and therefore, must SOURCES OF WATER POLLUTION protect it more than any other resource found on Earth. So how can we prevent water pollution? AGRICULTURE Here are some tips which you can do to lessen water pollution - Farm fields use big amount of chemicals such as fertilizers on a regular basis. The chemicals dissolve in rainwater. Runoff may carry some of the chemicals to 1. Proper waste disposal - do not pour oil or household nearby rivers or lakes. Dissolved chemicals causes an chemicals on the drain. Avoid spilling them on soil excessive amount of growth of water plants and because it can seep to the ground and might algae. contaminate the water. - This may result in dead zones within the water 2. Lesser use of garden chemicals - use compost or wherever nothing can live. Also, some of the chemicals organic fertilizers for your garden needs. If it is may seep in the ground and contaminate possible, grow plants that require lesser chemicals or groundwater. They may end up in water wells. fertilizer to grow. - If people consumed contaminated water, they may 3. Avoid pet and farm animal wastes to enter water get serious health problems. Waste (fecal matter) supply - the wastes may contain disease-causing from farm animals also can contaminate water. The bacteria. waste contains microorganisms that cause sickness. WASTES GENERATION AND EFFECTS William Rathje Source reduction is, on the face of it, perhaps the most INDUSTRY appealing of all the possible approaches to solid-waste management. - Many industries produce waste products that are toxic such as lead, arsenic, and mercury. Aside from these Three types of waste toxic chemicals, nuclear powerplants produce radioactive wastes that are cancerous and pose serious health problems. - Also, human activities may spill oil in the ocean and other bodies of water which can seep into the SOLID WASTES groundwater making it unsafe for human consumption. - are considered as the most common and most abundant type of wastes. - These may be in the form of food leftover, paper, plastics, wood, ashes, rubber, and metals. These are generated from different human activities. Examples and sources of solid wastes Examples and sources of gaseous wastes ✓ Disposal of excess food causes the generation of food ✓ A person’s use of materials such as plastics and metals refuse. Surprisingly, it constitutes a large percentage indirectly contributes to the increase of gaseous of solid wastes even if there is a global problem of wastes in the atmosphere. hunger. ✓ Improper garbage disposal of households, industries, ✓ Paper wastes come from businesses and homes as and commercial institutions promotes methane well. As a person uses more paper, more wastes are production. generated. ✓ The use of hairsprays and aerosols at home adds to ✓ A newspaper can be useful for a day but is usually the gaseous wastes in the atmosphere. disposed of when out of date. ✓ Garbage incineration produces harmful carbon ✓ When a person consumes pre-packaged products, oxides. solid wastes are generated. The excess packaging of ✓ Automobile usage is one of the major sources of products, such as food, electronics, and furniture, carbon monoxide wastes. contributes to the great amount of paper and plastic ✓ Using electricity has a part in generating gaseous wastes. wastes due to the fossil fuels used in the production of ✓ Constructions of different structures also contribute to energy. other types of solid wastes such as wood, cement, rubbers, metals, and ashes. EFFECTS OF WASTES TO HEALTH AND ENVIRONMENT LIQUID WASTES - The increase in the population of the world causes an increase in the number of wastes generated. Large usually come in the forms of wastewater, fats, oil and grease, amounts of wastes need to be properly disposed of household fluids, and mechanical oil. They are regularly every day. If these wastes are not properly managed generated because of constant human activities. More and disposed of, they will have negative effects not wastewater is generated as people use excessive water in only on the environment but also on the health of the activities such as household and industrial cleaning, watering of people. plants, and feeding animals. - Solid waste is the most abundant type of waste. It may be in the form of food refuse, paper, plastics, wood, ashes, rubber, and metals. Liquid waste usually Examples and sources of liquid wastes comes in the form of wastewater. Fats, oil and grease, household fluids, and mechanical oil are some of its examples. Finally, gaseous waste is usually produced ✓ Cooking using oils and lard contributes to liquid waste from the combustion of different materials. The most production. common examples include carbon monoxide, nitrogen ✓ Bleaches, liquid detergents, and insecticides that are oxides, methane, sulfur oxides, and aerosols. disposed of in drains are also liquid wastes. ✓ Disposed mechanical oils from car repair shops and car manufacturing sites also contribute to liquid wastes. EFFECTS OF SOLID WASTES TO ENVIRONMENT - Solid wastes end up in waterways that pollute water resources. GASEOUS WASTES - Floods are caused by improperly disposed wastes that block the drainages. Carbon oxides, nitrogen oxides, methane, sulfur oxides, and - Some non-biodegradable wastes can reach the aerosols are the most common type of gaseous wastes. They oceans. Marine animals sometimes see them as food are usually produced through the combustion of different and ingest these wastes. Sometimes, these wastes materials. Many of the materials we use are produced in affect the growth of marine animals. facilities that emit these gaseous wastes. EFFECTS OF LIQUID WASTES TO ENVIRONMENT EFFECTS OF GASEOUS WASTES TO HEALTH - Liquid wastes from solid wastes and chemicals - Gaseous wastes in the atmosphere are one of the produce leachate that seeps through the soil and primary causes of respiratory diseases in humans. water. It causes soil sterilization and water pollution. - Some of these wastes increase cancer risks and lung - Run-offs from farms that reach coasts, rivers, and weakening. lakes cause eutrophication. Eutrophication happens - Carbon monoxide, generated from exhausts, can when excess nutrients such as nitrates and phosphorus cause neurological dysfunctions and even death. go into water resources. These compounds cause algal blooms that overcrowd the water surface. - Chemical wastes and eutrophication due to run-offs both cause fish kills and death of other organisms. Simple waste management practices ✓ Avoid plastics ✓ Buy food that has minimal packaging EFFECTS OF GASEOUS WASTES TO ENVIRONMENT ✓ Compost your kitchen wastes ✓ Perform transactions electronically to reduce the use - Gas exhausts from automobiles and factories cause of paper acid rain when these wastes combine with the rain. ✓ Consider making soaps and detergents at home Acid rain destroys plants, buildings, and livelihoods. ✓ Repurpose other sturdy containers They also contaminate the soil and water resources. ✓ Donate items whenever possible - Methane from decomposing solid wastes contributes ✓ Reduce, reuse and recycle to greenhouse gases. - Chlorofluorocarbons from gaseous wastes cause the depletion of the ozone layer. The ozone layer is important because it protects us from the harmful rays of the sun. WEATHERING Physical Change refers to changes limited in the physical attributes or appearance of an object without changing its EFFECTS OF SOLID WASTES TO HEALTH chemical composition These includes changes in an objects' color, shape and texture. An example of this is cutting a paper. - Solid wastes contaminate water resources. The Cutting the paper changes its shape and size but does not contaminated water may cause gastrointestinal affect the chemical composition of paper, thus this is considered diseases. as physical change. - People residing near landfills experience skin diseases due to continuous contact with wastes. Chemical change is the type of change that is not only limited - Solid wastes, especially biodegradable ones, attract to its physical properties. This type of change involves changes rodents and flies that bring various diseases to in its chemical composition and the formation of new products. people. Common examples of chemical change include change in temperature, change in color, noticeable odor, formation of precipitate, effervescence etc. EFFECTS OF LIQUID WASTES TO HEALTH Earth's landforms and terrains are constantly being carved by natural geologic processes. No rock, no matter how hard it is, is - Liquid wastes such as mercury from mines and prone to change and degradation. Examples of these geologic hospitals cause poisoning in humans when they processes that helped shape the Earth's surface are weathering consume mercury-contaminated fishes. and erosion. These two processes always go side-by-side with - Shellfish contamination due to algal blooms may one another. cause poisoning in humans when consumed. - 3Strong chemicals that make up some liquid wastes distress the reproductive systems of humans, especially those of males. - Water poisoning also threatens humans because of liquid wastes in water resources. National Geographic Salt crystal growth - This type of weathering is quite similar to freeze- thaw. In this type of weathering, weathering is a process wherein rocks and minerals are broken water that contains dissolved salt penetrates cracks down and dissolved on the Earth's surface. This is aided by and crevices. As temperature rise, water will natural forces called agents of weathering such as water, ice, evaporate leaving the salt inside it. The crystal salt acids, salts, plants, animals and even changes in the inside the crevices will exert pressure and will cause temperature. the larger wedges. This commonly happens in place experiencing high temperature and evaporation rate Disintegration is a process that describes how large and even in rocks near seawater. masses of rocks and mechanically broken down into Hydration - In weathering by hydration, water smaller chunks or fragments. molecules will attach to crystalline structure of Decomposition is a process that describes changes in minerals. Water can join the host through hydration the chemical composition of rocks to form new causing the mineral to expand and leave through products. dehydration causing the mineral to shrink. The weathered rocks and other products of weathering such as clasts (broken fragments of rocks) are transported elsewhere in a process called erosion. CHEMICAL WEATHERING There are several types of weathering under two major In contrast with mechanical, chemical weathering is a type of categories, the mechanical weathering and chemical weathering caused by changes in chemical properties of weathering. Biological weathering, a type of weathering that minerals and rocks. Changes in the chemical composition of is caused by living organisms, can fall to both mechanical and rocks and minerals may also help break down rocks. chemical weathering. The products of chemical weathering are commonly stable at MECHANICAL WEATHERING the Earth's surface (just like metamorphic rocks, rocks formed through extreme heat and pressure). Chemical weathering is also called physical weathering and disaggregation, is most catalyzed by agents such as water, carbon dioxide and weathering that Involves the disintegration of rocks causing it to oxygen. break while retaining its chemical properties. Three Chemical Weathering Processes Types of Mechanical Weathering Oxidation - A process where oxygen (from water) Unloading - The type of mechanical weathering bonds with other elements from rock forming minerals caused by the expansion of the upper portion of a forming other substances that are more stable, lower block intrusive igneous rock. The expansion was malleability, larger volume and more distinct color. It caused by the differential pressure from the bottom commonly occurs to metals present in rocks such as of the block and the exposed strata. It is common for aluminum and iron. Oxygen bonds with these metals granitic rocks and rocks that lack internal bedding. forming aluminum and iron oxides. Thermal Expansion and Contraction - High Solution and Carbonation - Solution is the chemical temperature causes rock to expand while low process of dissolving rock-forming minerals in water. temperature causes rocks to contract (just like the In this reaction, mineral- forming ions are dissociated direct proportionality between temperature and and are carried away in the water. Some rocks volume in Charles' Law). The variation between containing mineral that are insoluble or slightly temperatures can cause rocks to crack. This type of insoluble undergoes solution process when water is weathering is common for places that experience acidic. Lichens and mosses aid in the solution process extreme swings in daily temperatures. of such types of rocks by secreting acidic substances that readily mix with water from precipitation. Freeze-Thaw Weathering - Also called ice wedging, Carbonation is the chemical weathering process that this is a type of mechanical weathering that happens decomposes rocks through the aid of water and when water penetrates rock cracks. As temperature carbon dioxide. This process is common to rocks drops, the water freezes and expands causing the containing carbonates (CO) such as limestone. widening of cracks. Continuous freezing and thawing will cause the crevices to expand larger which will further lead to breaking the rock.  Hydrolysis - In this process, water molecules alone, DIFFERENTIAL WEATHERING AND EROSION rather than oxygen and carbon dioxide in it, react with the components of rock-forming minerals. This is If a landscape contains a variety of rocks, some rocks are more commonly aided by the dissociation of the hydronium - susceptible to weathering and some are more resistant. In this ion (H) and hydroxyl (OH) binding with other elements case, more susceptible rocks undergo weathering faster and and compounds in rocks. This process is different from rock fragments are transported through the process of erosion. the process of hydration. In hydration, water moves in and out of the mineral causing the rock to shrink, swell This variability in the rate of weathering in rocks in a landform and break without changing its chemical properties. In is called differential weathering. hydrolysis, ions from water combine with other elements/compounds forming new products. The effect of differential weathering is highly visible to some landforms. Highly resistant rocks tend to -withstand weathering VARIABILITY IN WEATHERING leading to the formation of high-rise landforms such as cliffs and mountains. Susceptible rocks are easily eroded and In this part of the module, the factors affecting the rate, extent transported leading to the formation of gentler slopes, valleys and type of weathering will be discussed. and even subdued hills. Did you know that? Bowen's Reaction Series is a tool used to describe the crystallization sequence of common igneous silicate minerals DEFORMATION OF EARTH'S CRUST: FOLDING AND shows the crystallization temperature for each mineral. FAULTING Minerals at top have the highest crystallization temperature which -means that they will crystallize first from a cooling magma. Itis the work of a petrologist named Norman L Bowen. INTROUCTION TO DEFORMATION Climate areas that are cold and dry tend to have Deformation refers to the changes in volume and or shape of slow rates of chemical weathering and weathering is rocks as they are squeezed by compressional forces or mostly physical, chemical weathering is most active in stretched by the tensional forces. areas with high temperature and rainfall. Rock Type Rock susceptibility on weathering is also Stress is the force per unit area applied on the rock dependent on the rock type. Some rocks contain minerals that are highly susceptible to weathering Strain is the change in shape or volume of the rock that while there are rocks that contain minerals that are experienced stress. highly resistant to weathering. In the Bowen's reaction series, minerals that crystallize first are susceptible and minerals crystallize last are more resistant more that. Types of stress and resulting strain Rock Structure rate of weathering is affected by the presence of joints, folds, faults, bedding planes through which agents of weathering enter a rock mass. Tensional stress involves forces pulling in opposite Highly jointed/ fractured rocks disintegrate faster directions, which results in strain that stretches into thin than a solid mass of rock of the same dimension rocks. Topography Physical weathering occurs more quickly Compressional stress involves forces pushing to highly elevated areas with steep slope due to the together or the stress that results from the shortening help of gravity. In areas with gentle slopes, water in one dimension of an elastic body due to oppositely may stay longer on the surface which causes chemical directed collinear forces tends to crush it. weathering to occur more quickly Shear stress involves transverse forces that result in Time The length of exposure to agents of weathering deformation of material by slippage along a plane affects the rate of erosion. Parts of rock boulders that of planes parallel to the imposed stress or regions of are exposed are more susceptible to weathering material moving past each other. because of its exposure to water, air and other agents of weathering Also, some rocks submerged in water (both freshwater and seawater) or are commonly in contact with water are more prone to weathering processes such as hydration and hydrolysis. Stress and strain STRIKE-SLIP FAULTING involves movement chiefly in the horizontal direction (sideways or laterally) The resulting strain in rocks can be classified into elastic, ductile or brittle depending on the stress applied in the material. A. Right-Lateral Strike-Slip Fault sideways movement of fault to the right. Example: San Andreas Fault in California U.S.A. Elastic deformation is strain that is reversible after a B. Left-Lateral Strike-Slip Fault if the other block moved to stress is released. your left, then the fault is a left- lateral strike-slip fault. Ductile deformation occurs when enough stress is Example: Philippine Fault applied to the material that causes changes in shape and no longer be able to return to its original shape. Yield point is the point at which elastic deformation is surpassed and strain becomes permanent. Brittle deformation materials respond to stress by Philippine Fault is an example of Strike-Slip Fault. In reality, breaking and fracturing. the Philippine Fault consists of several faults parallel to one another and it is called Philippine Fault Zone. The fault extends from Luzon through the eastern part of the Visayas, down to Rocks that are subjected to forces may deform in two ways. eastern Mindanao FRACTURE (BREAK) that happens in the uppermost part of the crust which tends to break when subjected to compressional or ENDOGENIC PROCESSES METAMORPHISM tensional forces. You have learned from the previous lesson that rocks/minerals become unstable and change into another mineral as a response to heat, pressure and chemically active fluids. This Two types of fractures process is known as metamorphism through which pre-exiting rocks transformed into metamorphic rocks. faults that breaks along when there is considerable movement Factors controlling the mineral assemblage of metamorphic rocks. joints are those breaks where there is little or no movement. ◆ Bulk composition of the original rock ◆ Attained pressure/temperature during metamorphism FOLD (BEND) happens deep within the crust and the rocks do not break the way they do at the earth's surface. ◆ Composition of fluid phase that was present during metamorphism Rocks bend and go out of shape. Foliation generally caused by repetitive layering of sheet Hanging wall is a block of rocks resting on the fault silicates (silica minerals with sheet-like structures) such as clay plane. minerals, mica and chlorite. Footwall is a block below the fault plane. Classification of Metamorphic Rocks Types of faults DIP-SLIP FAULTING involves the movement of blocks of rocks mainly in vertical direction, move up and down. FOLIATED A. Normal fault formed when the crust is stretched or pulled - it shows a layered or banded appearance due to the apart by forces in opposing directions and when the hanging parallel alignment of elongated or platy minerals. wall moves down with respect to the footwall Common foliated metamorphic rocks are slate, phyllite, schists, and gneiss. B. Reverse fault when the crust is squeezed or compressed, the - Gneiss (pronounced, nice). The foliation in gneiss is hanging moves up relative to the footwall striking Light-colored minerals segregate from dark ones, forming light and dark layers alternating with one another. NON-FOLIATED Wegener aligned his theory with references from past authors with similar ideas like those of Eduard Suess (1831-1914) who do not exhibit foliation because they are commonly made of is better known to have proposed the existence of Tethys Sea minerals which are neither platy or elongated. Example: the only recognized body of water those ancient time, as he Marble, Quartzite recognized existence of Gondwanaland. Types of Metamorphism Did you know? ◆ Contact an intrusion of hot, molten magma will change the Wegener's theory was not widely accepted by the scientific rock when it comes in contact. Do not show foliation. community for many years. It was initially dismissed because it did not offer an acceptable hypothesis explaining the ◆ Regional metamorphism large scale movements of Earth's movement of the continent. Wegener could not explain what crust cause a vast region of rock to sink into the Earth force was driving the motion of the but Wegener provided which experiences increased heat and pressure. Develop strong evidence to support his Continental Drift Theory. foliation or layered texture. PLATE TECTONICS EVIDENCE OF CONTINENTAL DRIFT THEORY In 1912, geophysicist and a German meteorologist Alfred The apparent fit of the continents Wegener (1880-1930) developed the Continental Drift Theory that explains how continents shift position on Earth's surface. Continental drift is the gradual movement of the continents over The coastlines of the continents appear to fit together like the time. The upper layer of the crust is broken down plates, which pieces of puzzle, The apparent fit is even better when sit on a molten rock. The movement of this lower molten layer, submerged coastlines are examined. In this diagram, significant called plate tectonics, causes the plates to shift. overlap of the coastlines occurs only in the shaded areas because underwater sediments are extensively deposited. Wegener theorized that all the continents were once interconnected from a supergiant land mass, which he called Pangaea. Fossil Correlation According to the hypothesis, Pangaea broke apart and each land mass drifted away from each other in different locations. Identical fossils have been found in the rocks found on At some point between 275 and 175 million years ago, coastlines the ocean. Pangaea began to separate. - Mesosaurus lived in Africa and South America - Glossopteris lived in southern continents - Cynognathus lived in Africa and South America Initially, two giant continents were formed: - Lystrosaurus lived in Africa Antarctica, India - Laurasia which comprised the northern continents of today's times - Gondwanaland which comprised the continents in the Rock and Mountain Correlation present southern hemisphere. Identical rocks and mountain structures have been found. Paleoclimate Data/Past Climate Data The slow process of fragmentation and drifting continued until the continents eventually reached their current position. The Coal and compacted sediments of tropical plants have been continents are not at rest, they are always moving and over found in cold regions and glacial evidence (Glacial time will move and drift into entirely new continents over the Striations/Scratches) have been found in warm regions. next hundred years.  Seafloor Spreading Model Evidence to Support the CDT Scientists estimated that the continents move anywhere from Evidence from Landforms or The Continental Jigsaw one centimeter to several inches per year. If the appearance of the Earth is drastically changing over time, are there any - The shapes of the continents seemed to fit together. changes in the overall volume and size of the Earth? Mountain ranges and other features also lined up. - South America and Africa fit together. Seafloor spreading is a continuous process where tensional - India, Antarctica and Australia match one another. forces on both sides of the plates caused them to constantly - Eurasia and North America completed the puzzle in move apart. Magma rises to the surface from the mantle. In the North. time, the magma is cooled by seawater and forms the oceanic crust. New rocks then form in this area. Since the newer rocks are younger in features, scientists are able to determine areas Evidence from Fossils of seafloor spreading because of the types and compositions of new rocks on areas. Rocks from the separated plates would - Fossils from one continent matched fossil from other have similar rock types and compositions usually of continents. sedimentary type while the area at the center have mostly - Wegener used both plant and animal fossils. igneous type. - Fossilized leaves of an extinct plant Glossopteris were found on a 250- million-year-old rocks. These Usually, seafloor spreading happens along mid- ocean ridges. fossils were in the continents of South Africa, Australia, Elsewhere, trenches are formed where one plates slides India and Antarctica which are now separated to beneath another because the older seafloor rock eventually each other by wide oceans. descends into trenches and is removed. Therefore, there is no - Mesosaurus: a freshwater swimming reptile found in change in the overall volume and size of Earth. If the crust is Africa and South America expanding along the oceanic ridges, it must be shrinking somewhere else. Evidence from Climate The concept of seafloor spreading was developed by geologists Harold Hess (1895- 1982) and Robert Dietz (1914- - Wegener looked at certain areas on Earth and their 1995). They coined the term "seafloor spreading" and showed climates it aligned with the unaccepted ideas of continental drift. - He noted that the fossils he found on certain sections of Earth did not the current climate. CONTINENTAL DRIFT THEORY SEAFLOOR SPREADING ALFRED WEGENER The mechanism that operates along the ocean ridge system to create new floor is called seafloor spreading. - As a young scientist, Wegener was curious about Earth's continents. - In 1910, Wegener formed a hypothesis which stated that 250 million years ago, all Harry Hess an American geologist together with Robert Dietz the continents were once joined together in a giant presented this hypothesis and he proposed that the seafloor is landmass. not permanent but is continuously being renewed. - He named this landmass PANGAEA. - this giant supercontinent was surrounded by a single - Hess theorized that the ocean ridges are located giant sea known as the Panthalassa. above upwelling convection cells in the mantle. - According to Wegener, Pangaea split up into smaller - The theory of the seafloor spreading provided the continents. mechanism for the continental drift. - Laurasia and Gondwanaland Findings that Support the Seafloor Spreading - Rocks are younger at the mid-ocean ridge Theory of Continental Drift, which states that parts of the - Sediments are thinner at the ridge Earth's crust slowly drift atop a liquid core. The giant landmass, - Rocks at the ocean floor are younger than those at the Pangaea, drifted apart and formed the seven known continents continents. today.