Earth's Structure

3 types of convergent boundaries

oceanic-oceanic, oceanic-continental, continental-continental

lava flow

the spread of lava as it pours out of a vent

mineral vs. rocks

Minerals are different from rocks, which are made up of one or more minerals and have a range of chemical compositions rather than one specific formula. Minerals in rocks can be distinctly visible or can be mixed together and difficult to distinguish from one another.

Stone Mountain is a granite rock dome in Stone Mountain State Park in North Carolina near the Virginia border. The mountain's surface is indented with rounded, irregularly shaped pit depressions in the rock. When the water freezes and thaws, the rock surface breaks apart. When a tiny particle is loosened, chemically or mechanically, but stays in the pit of its rock, the process is called:

Weathering is the term used when a particle is loosened but does not include any movement.

oceanic-oceanic convergence

When two oceanic plates converge, the denser plate subducts below the other. volcanic island arcs magma erupts through oceanic plate creating volcanoes that create islands deep trenches due to subduction large earthquakes

mineral

a naturally occurring, solid, inorganic element or compound that is formed by natural processes, has a limited range of possible chemical composition, and has a definite arrangement of atoms. • naturally occurring • elements or compounds • specific chemical formula • definite shape • definite volume • inorganic • crystalline structure • start out small and, with sufficient time and under appropriate conditions, grow into distinctive well-defined crystals. • examples: quartz, mica, pyrite, gypsum, halite

While looking for rocks you are able to distinguish them from minerals because minerals have ______ chemical composition.

fixed

A cause of erosion that moves particles like soil, sand, and even some rocks rapidly for great horizontal distances is______.

flowing water

processes that form igneous rocks

formed by lava or magma. Lava: lava on the surface of the Earth cools quickly. fine grained because crystals do not have time to grow. example: basalt Magma: magma cools slowly underground. allows larger crystals to form. individual minerals can be distinguished from one another. example: granite

Evidence of snails, brachiopods, and trilobites preserved in rock demonstrate that the area was once part of a shallow tropical sea. What are these physical items called?

fossils

wind erosion

occurs when soil particles are lifted off the ground and transported by wind. • wind must be strong enough to overcome the cohesive and gravitational forces that keep the particles on the ground. • human activities can accelerate wind erosion (farming practices & dust bowl of 1930s) • Vegetation reduces wind erosion, so the most wind erosion will occur in a barren landscape.

oceanic and continental divergent plate boundary

oceanic most divergent boundaries lie under the oceans, on the seafloor between continents. As the plates move apart, magma rises up from the mantle to fill the gap. Lava erupts to form a long submarine volcano—the mid-ocean ridge. The magma and lava solidify and become part of each plate. New ocean crust forms and the plates grow at divergent ocean-ocean boundaries. continental can also occur within a continent. continental crust thins so much that mantle rocks are extremely close to the surface. The mantle rocks melt and erupt to form new oceanic crust. Eventually, the low valley fills with ocean water and a new ocean forms. a continental rift becomes a seafloor spreading zone.

Aeolian processes

erosion, transport and deposition by the wind

Unconformity

A buried erosional surface • Rock or sediment was eroded rather than deposited during this time. • A sedimentary rock formation below an unconformity is generally thinner than it would be if the unconformity did not exist because erosion of the rock formation removes material. • The presence of an unconformity suggests a period for which no rock record exists. • An unconformity means a lack of information. • Unconformities are caused by erosion.

analog

A close approximation, or direct analogy, of the long-term behavior of materials and processes found in a geologic feature • Geologists frequently use modern-day analogs to help determine how rocks were formed • The progression of sediments on a marine shelf is an example of a modern-day analog. • Physical and chemical clues can be found in sedimentary, metamorphic, and igneous rocks.

About 500 million years ago, some of the ancient oceanic crust near a national park lifted in an area where one oceanic plate was pushed beneath another. Which type of boundary did this lifting occur at?

A convergent plate boundary is an area where two tectonic plates collide.

inner core

A dense sphere of solid iron and nickel at the center of Earth structure/ composition: • metal • solid ball of nickel-iron alloy • solid due to extreme pressure. • densest hottest layer • as hot as the surface as the sun

Fossil

A fossil is the preserved remains or traces of a dead organism. Fossils are the remains or traces of animals, plants, or other organisms that have been preserved within sedimentary rocks like limestone. Fossilization can occur when organisms are buried quickly after death and preserved with the help of mineral-rich water.

glaciers

A glacier is a slowly moving mass of ice formed by the accumulation and compaction of snow • flows • compacted snow turns to ice • form in permanent snowfields • gravity pulls the ice downhill • white when freshly formed, then blue as ice is compressed and air forced out. • equilibrium if new snow replenishes what melts as flows downhill • calving creates iceberg • cracks/crevasses due to unequal movement

geologic time scale

A history of Earth representing the different time periods of its geological evolution • Divided into eons, eras, periods, epochs/ages • The first single-celled organisms are thought to have evolved about 4 billion years ago. • The first complex single-celled organisms are thought to have evolved about 1.8 billion years ago. • Dinosaurs went extinct about 65 million years ago • The rise of human civilization began about 8,000 years ago.

outer core

A layer of molten iron and nickel that surrounds the inner core of Earth structure/ composition: • metal, mostly iron • liquid • has average temperatures of about 5000°C

ring of fire

A major belt of volcanoes that rims the Pacific Ocean

rocks

A naturally formed aggregate, or mixture, of minerals; have varied chemical compositions • made up of one or more minerals • have a range of chemical compositions rather than one specific formula • examples: Granite (contains quartz) • classified by how they form: igneous, sedimentary, and metamorphic

transform boundary

A plate boundary defined by each plate grinding past one another (move past each other in opposite directions) • connect sections of divergent and convergent boundaries. • most under oceans, but some occur within the continental crust • no subduction/ volcanoes uncommon • earthquakes

divergent boundary

A plate boundary defined by the plates moving apart from one another

convergent boundary

A plate boundary defined by the plates pushing into one another. (move toward each other.)

principle of superposition

A principle stating that in any sequence of undeformed sedimentary rocks, each bed is younger than the one below it and older than the one above it.

principle of cross-cutting relationships

A principle used to determine the relative ages of different rocks: if a rock, fault, or other feature cuts through a rock layer, that rock layer must have been preexisting in order to have been cut through • According to the principle of superposition, the bottom layer formed first and is, therefore, oldest; the middle layers were formed afterward; and the top layer formed last. The dike cutting across all five bottom layers, but not the top layer, shows it was formed after the first five layers, but not the top layer, making it the second-youngest layer.

Lithosphere

A rigid, brittle layer made up of the uppermost part of the mantle and the crust. • broken into tectonic plates • floating on the asthenosphere

earthquakes

A sudden shaking of the ground that occurs when rocks in Earth's crust break suddenly, releasing energy. • about 90% of the world's earthquakes occur around the edge of the Pacific Ocean, which includes the west coast of the Americas and the east coast of Asia • Earthquakes occur when potential energy stored in the crust of Earth is suddenly released.

alluvial fan

A wide, sloping deposit of sediment formed where a stream leaves a mountain range (canyon) • rapid flow in the canyon picks up sediment • upon exiting the canyon flow slows • material is deposited in a fan shape

meanders

A winding, looping curve in the course of a river on soft, flat flood plain • produced as rivers erode and deposit sediment • form as a river erodes its outer bank while simultaneously depositing sediment along the inner edge of the meander. • outside of the river has faster flow so it erodes, inside has a slower flow so it drops sediment Pronounced curves in a river are called meanders.

Cenozoic Era

Age of the Mammals (known as the age of mammals, which thrived in the wake of the dinosaurs' extinction, despite the fact that birds have outnumbered mammals by two to one throughout much of this era.) • 66 million years ago, • mammals diversified and ruled the surface of the Earth • first primates appeared • Evolution of hominids

Mesozoic Era

Age of the dinosaurs their extinction at the end of this era is believed to be caused by a large asteroid that hit Earth • spanned from 252 to 66 million years ago • The era began and ended with major extinction events • Triassic, Jurassic, and Cretaceous Periods • dinosaurs flourish • birds, mammals, and flowering plants developed • Breakup of Pangaea

volcano

An opening in Earth's crust through which molten rock and gases erupt on Earth's surface • Most occur in the ring of fire. • Most volcanoes are located along the edges of some continents or in chains off the coast of continents. • Occur at plate boundaries (with a few exceptions): ○ divergent boundaries ○ ocean-ocean convergent boundaries ○ ocean-continental convergent boundaries • fissure in Earth's surface • magma below ground, lava above ground • solidifies to form Igneous rocks, like basalt

introduction to Earth's structure tectonics

Another process the Earth undergoes is tectonic movement. The crust of the Earth is actually a number of different large, interlocking plates that are moving against each other at various points on Earth. The theory of plate tectonics provides a tool for explaining many of Earth's features and processes. Areas of high volcanic and earthquake activity coincide with boundaries of the plates and are one of the main focal points of tectonic study.

introduction to Earth's structure rocks and minerals

As you continue to learn about Earth's composition, you will see that Earth's crust and mantle are made of rocks and minerals, with quartz being the most common mineral in Earth's crust. Earth's rocks can be classified into three types based on how they were formed: sedimentary, igneous, and metamorphic. Rocks and minerals have many measurable properties that scientists study in order to understand what Earth was like hundreds of thousands to millions of years ago. Scientists do this using a geologic time scale to represent the history of Earth. This time scale is based on discoveries made using the rock record, which preserves many clues about Earth's history, organisms, and past environmental conditions as fossils. Fossils are the remains or traces of animals, plants, or other organisms that have been preserved as hard minerals. The presence of fossils can reveal what kinds of life were present during different geologic periods, how long various species survived, and how organisms evolved over time.

introduction to Earth's structure processes

Beyond its seasonal pattern, Earth is subject to a number of processes that form and shape it. Structurally, Earth is composed of layers that vary in composition and characteristics. The changes that occur within and between these layers are what create the mountains, volcanoes, and other formations in the Earth's crust. The most unique characteristic of Earth is that, unlike the other planets in this solar system, it has flowing water. Flowing water, of course, is one of the main reasons Earth can support life; however, water is also responsible for much of the way Earth's landscape has been shaped over time. Earth's surface is constantly changing due to ongoing processes such as weathering, erosion, and deposition, and flowing water is the most powerful agent of the erosion process.

Calcite is a very common component of Earth's crust. Calcite is classified as a:

Calcite is a mineral composed of the element calcium in the form of a specific chemical compound.

how processes of weathering occur

Chemical and physical weathering often work together. For example, physical weathering may break a rock into smaller pieces. That increases the surface area of the rocks, allowing chemical reactions to happen more quickly. Examples: • changes in temperature can cause rocks to expand and contract. • liquid water that seeps into cracks in a rock can break the rock apart when it freezes and expands. • tree roots can break apart a rock as they grew • Rainwater is a very weak acid that can react with some minerals and dissolve them more readily. • Water and oxygen react with certain minerals to rust the rock

Evidence that supports plate tectonic theory

Comparison of continent shapes The fossil record GPS tracking of continent movement

The tallest dunes in North America are the shifting, golden Great Sand Dunes at the base of the Sangre de Cristo Mountains near Alamosa, Colorado, and were designated as a national park in 2000. The huge dunes of sand that lack any covering vegetation were formed when sand carried by the Rio Grande River and its tributaries was placed in the river valley by a process known as what?

Deposition includes the buildup of sediment carried by water in rivers that slow as they drop from steep mountains into a valley.

how processes of deposition occur

Deposition occurs when the energy of the transporting agent is no longer sufficient to overcome the opposing effects of the weight of the material and the friction or drag between the material and the surface it is traveling over or through, causing the material to drop out of the flow. Water, wind, and gravity will deposit large, heavy materials close to the source but will carry finer, lighter particles a longer distance and deposit them farther away.

Thousands of delicately carved spires known as "hoodoos" rise in brilliant rose pink color in Bryce Canyon National Park in Utah. Which process occurs to shape and etch the hoodoos from the pink cliffs as the dissolved and fractured rock is removed from the cliffs?

Erosion is the removal of dissolved and fractured materials from their original location.

moraines

Features called moraines are created when glaciers plow up mounds of dirt and rock in front of them and along their sides, like bulldozers. These mounds remain behind long after the glacier is gone.

how water shapes the landscape

Flowing water is the most influential and pervasive agent of erosion. Rivers • remove sediment and carry away • the faster a flow is, the larger and heavier the particles are that it can carry. • heavy objects fall out of flow first • smallest objects deposited last • creates: river delta, alluvial fan, natural levees, marches called back swamps Oceans •waves are able to scour rock and sediment. tides move the sediment away from shore Glaciers • sediment being moved by a slow-moving mass of ice • The solid state of ice makes it a more effective agent of erosion than liquid water; it is able to transport material of nearly any size, including boulders.

How fossils are used

Fossils can be used as a tool to learn about Earth's history. Fossils can reveal what kinds of life were present during different geologic periods, how long various species survived, and how organisms evolved over time. Help geologists learn about extinction events, which are marked by abrupt changes in fossil prevalence. Fossils also store information about past climates and environmental conditions

The most precise and most direct method to monitor the motion of the continents is by:

GPS (global positioning system) satellites are able to measure the movement of continental plates accurately and directly.

Landslides are a rapid erosion in which large amounts of weathered rock suddenly fall down a cliff or mountainside because of:

Gravity is the force that causes weathered rocks to move down a cliff or mountainside that erodes.

Summary

In these lessons, you learned that Earth is much more than a solid, uniform sphere. Earth's interior is divided into layers: the crust, the mantle, the outer core, and the inner core. Each layer has its own unique composition—the crust is the thinnest layer, the mantle is the thickest layer and is made of solid rock that is so hot it can flow under stress, the outer core is made of liquid iron and nickel, and the inner core is made of solid iron and nickel. These lessons also reviewed the different ways that Earth's crust can change. In particular, you learned about weathering, erosion, and deposition, which are important processes that shape Earth's surface. You learned about different agents of erosion, such as water, wind, and glaciers. You also learned about the various processes that produce different kinds of rocks: the rock cycle. Earth is more than 4.5 billion years old, and it has gone through significant changes since it formed. Scientists learn about Earth's past by studying the rock and fossil record, and you learned how fossils and rock layers give information about Earth's history. Earth is a dynamic planet, and the crust is constantly changing. The theory of plate tectonics helps to explain many of these changes. According to the theory of plate tectonics, Earth's crust is broken up into large plates that are in constant motion. Most earthquakes and volcanoes occur where these plates collide with each other. Where plates spread away from each other, new crust is formed.

lava

Magma that reaches Earth's surface

Western Newfoundland is one of the few places on Earth where oceanic crust can be observed on dry land. Oceanic crust forms when magma wells up from the mantle at which type of tectonic plate boundary?

Magma wells up from the mantle at divergent plate boundaries where tectonic plates are pulling apart.

Dinosaurs lived in the _______era.

Mesozoic

using analogs for rock records

Modern shorelines show that mud, silt, and sand are laid down in a specific pattern. As sea levels rise this pattern continues in a new place. Because of this pattern, geologists can look at rocks and know how and where they formed. • sandstone formed near a shore • mudstone formed in slightly deeper water • limestone formed in deep water

magma

Molten rock beneath the earth's surface

Areas with an increased risk of both earthquakes and volcanic activity are located:

Near the convergent tectonic plate boundaries

In order for a dune to form, it is necessary that _____ be present to cause deposition of the sand.

Obstacles reduce the ability of the wind to carry sand and sediment and promote its deposition to form dunes.

In the ______ era, one of largest scale diversifications of life forms occurred and resulted in many species of fish, reptiles, and invertebrates.

Paleozoic

The Tablelands in Grand Morne Park are composed largely of peridotite. Peridotite is a mixture of two silicate compounds: olivine and pyroxene. Which type of substance is peridotite?

Peridotite contains a mixture of two minerals and is considered a rock.

Paleozoic Era

Plants and animals developed, but 95% of all life on Earth disappeared at the end of this period • The Paleozoic, from approximately 541 to 252 million years ago, was a time of great change on Earth. • Rapid diversification of life. It included the greatest diversification of life Earth has seen. • Evolution of multicelled organisms • Fish, arthropods, amphibians, and reptiles all evolved during this time. • land plants appear

How rivers shape the landscape

Rivers can be powerful enough to carve valleys as deep as the Grand Canyon through erosion. Rivers deposit the sediment the eroded and create deltas. • transport sediment • high to low elevation • reach the ocean

Igneous

Rocks formed by lava or magma; molten rock, or lava, cools quickly into rock when it erupts onto Earth's surface • originates deep inside the Earth • They form large crystals when formed underground and microscopic or no crystals when formed on the surface.

sedimentary

Rocks made up of weathered particles, such as sand, silt, clay, gravel, cobbles, or even occasionally boulders, that have been cemented together into hard rock • originates as detritus (loose sediment) formed from wind and water erosion • forms as detritus accumulates and compacts to a solid mass • often easy to identify because of their visible layers that are formed by the deposition of layers of sediment on top of each other

Metamorphic

Rocks that have been changed from their original form and typically occur when a rock is partially buried and exposed to elevated temperatures and pressures that are not extreme enough to completely melt the rock • forms as result of extreme pressure and/or temperature • can alter and change pre-existing, older rocks • can begin as either igneous or sedimentary rocks • They may contain distorted banding called foliation.

chemical weathering

The alteration or breakdown of rock or soil that occurs when a rock's composition changes • changes the composition of rock • usually the result of water which is a weak acid, reacting with minerals that are easily dissolved by water • decaying plants also create acidic environment

physical weathering

The alteration or breakdown of rock or soil that results from changes in temperature or pressure • result of mechanical processes • breaks into smaller pieces • does NOT change chemical composition • example: freeze/thaw cycle

Geological Eons

The broadest time interval of Earth's history is called an eon There are four eons: Hadean, Archean, Proterozoic, and Phanerozoic. Hadean Eon Archean Eon Proterozoic Eon • the first three are commonly lumped together into the Precambrian era Phanerozoic Eon ○ Cenozoic Era (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian Periods) ○ Mesozoic Era (Triassic, Jurassic, and Cretaceous Periods) ○ Paleozoic Era (Tertiary and Quaternary Periods)

pyroclastic flow

The expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption • contains dense gases, ashes, and fragmented rock that flow down the side of the volcano. • ashes and lighter materials can rise up into the atmosphere.

mantle

The layer beneath the crust, and the thickest layer of the Earth structure/ composition: • hot, solid rock • very small portion of the mantle, near the region where the crust and mantle meet, is soft and able to flow. • Due to the mantle's greater density, the continental and oceanic crust "float" on the soft part of the mantle. • The mantle comprises over 84% of Earth's volume and is over 2900 km thick. • Its temperature varies from about 500°C for the magma at its outer boundary with the crust, to about 4000°C at its inner boundary with the outer core of Earth.

erosion

The mechanism responsible for the transportation or removal of material. • weathering breaks the material down and erosion removes this material • agents of erosion: water, glaciers, wind, or gravity.

Phanerozoic Eon

The most recent eon, an interval of time from 542 Ma to the present. • 3 eras: Paleozoic, Mesozoic, and Cenozoic

oceanic-continental convergence

The ocean plate sinks under the continent and into the mantle below in a process known as subduction. causes volcanic mountains mixing water with hot mantle rock. melts mantle. magma rises and erupts through continental plate creates trench forms when oceanic plate subducts. some of the deepest places on Earth's surface earthquakes huge pieces of crust colliding with each other, they store a great deal of energy. This energy is typically released during large earthquakes. Most deep and powerful earthquakes happen at convergent boundaries.

crust

The outermost rocky shell at the surface of Earth structure/ composition: • rock • thinnest layer (1% of Earth's total volume) • brittle

weathering

The physical or chemical breakdown of rock or soil. • breakdown of a material in place • forms sediment • 2 types: chemical and physical weathering

sea-floor spreading

The process by which molten material adds new oceanic crust to the ocean floor. • key supporting evidence in the form of "magnetic stripes." When lava erupts, magnetic minerals in the lava align with Earth's magnetic field. Field reverses every few hundred thousand years,

till

The sediments deposited directly by a glacier

asthenosphere

The soft layer of the mantle on which the lithosphere floats. • partially molten top layer of the mantle

Theory of Plate Tectonics

The theory that pieces of Earth's outer layer are in constant motion. • The uppermost layer of Earth consists of several tectonic plates that float on Earth's mantle. • Seafloor spreading, the locations of earthquakes and volcanoes, fossils, climate indicators, and many other lines of evidence have helped scientists develop the modern theory of plate tectonics • All of Earth's continents were once joined together. • The tectonic plates move a few centimeters per year. • Energy from the decay of radioactive atoms provides some of the thermal energy that drives plate motion. • Differences in temperature cause differences in density, which result in convection currents within the mantle. These differences in temperature within Earth and within the plates result in processes that move plates. • Sinking plates at subduction zones also help pull the plates along.

rock cycle

The various processes that change rocks from one form to another • The rocks that make up Earth's crust are constantly changing. • Weathering, erosion, and deposition form sedimentary rocks. • Extreme heat can melt rocks to form magma or lava; when the melted rock cools, it forms igneous rock. • Heat and pressure can change the mineral makeup of the rock and change it into a metamorphic rock. • A cycle with no beginning or end

river valley

Valleys form when a river cuts down into the underlying bedrock. River erosion typically forms sharp, "V"-shaped valleys that have steep sides and a narrow bottom. The Grand Canyon is an example of a river valley. • formed by erosion • flow of rivers and streams • weathering and erosion of bedrock A large river will carve out large swaths of land to form a river valley as it flows down an elevation.

Relationship between Plate Boundaries, Volcanoes, and Earthquakes

Volcanoes • common at oceanic-oceanic and oceanic-continental convergent boundaries • common at oceanic and continental divergent boundaries • not common at transform boundaries Earthquakes • common at convergent boundaries because of the enormous forces involved when two plates collide with each other. most powerful earthquakes occur along convergent boundaries. • power quakes can occur at transform boundaries • can occur at divergent boundaries, tend to be weak. Ring of Fire • a significant portion of volcanic eruptions and earthquakes occur along the Ring of Fire. The Ring of Fire exists because most of the plate boundaries along the edges of the Pacific Ocean are convergent boundaries.

glacier valley

characteristics: U shaped process of formation: Valleys are formed as glaciers flow over rock, slowly weathering and eroding material and creating a deeper path for their flow. • glacier weathers and erodes a river valley • glacier eventually retreats

The movement of tectonic plates toward each other occurs at ______ boundaries.

convergent

Layers of the Earth

crust, mantle, outer core, inner core

river delta

deposits of sand and soil at the mouth of a river • A river delta forms from the deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water such as an ocean or lake. • deposits heaviest material closest to shore • lighter material carried further out to sea • forms a triangle-shaped deposit A delta is formed at the mouth of a river when sediment deposits as the river current dissipates into a large nonflowing body of water.

3 types of plate boundaries

divergent, convergent, transform

Deposition is the process in which soil, sediment, or rocks are added to a landform after being ______ by wind, liquid water, or glaciers.

eroded

Both glaciers and rivers may transport dirt and rock, a process called:

erosion

sand dunes

hills of sand shaped by the wind • An example of the aeolian process requiring the same three basic elements for formation: a large quantity of loose and unvegetated sand, wind, and an obstacle • formed through wind deposition

3 types of rocks

igneous, sedimentary, metamorphic • Because rocks are mixtures, their compositions can vary, so they are classified based on how they form instead of on their composition.

Crustal rock floats on mantle rock because crustal rock is:

less dense

When divergent plates move away from each other, the space between them gets filled with _________, which rises to the surface of the oceanic crust, cools, and forms mid-oceanic ridges.

magma

how rocks change one form to another

melting rocks can melt and become magma. magna cools and creates new igneous rock weathering and erosion rocks can be broken down into sediments and cemented together to form sedimentary rocks heat and pressure rocks can be exposed to high temperature and pressure that cause the minerals in them to change and become metamorphic rocks

Gros Morne Mountain is capped with quartzite, a hard rock that was formed when sandstone was exposed to extreme heat and pressure. Which type of rock is quartzite?

metamorphic

Olivine compounds contain a fixed ratio of silicate (SiO4) and magnesium or iron. Forsterite (Mg2SiO4) is an olivine containing magnesium, and fayalite (Fe2SiO4) is an olivine containing iron. What are olivines?

mineral

how glaciers shape the landscape

responsible for many different erosive and depositional landforms • weather, erode and deposit material • glacial deposits can consist of a diverse mix of clay, sand, gravel, and boulders. • create moraines • carve rock on a massive scale

how principles of superposition and crosscutting relationships allow geologists to learn about the history of an area by reading rock layers

rocks are often arranged in layers. by examining the layers geologist make insights. allowed us to chart the history of our planet • sedimentary rock could mean was under water • igneous rock is sign of volcanic activity • can tell relative age by using principles of superposition and crosscutting relationships • unconformities (show periods of erosion) and fossils show conditions at the time

types of volcanos

shield, cinder cone, composite

continental drift

the gradual movement of the continents across the earth's surface through geological time. • Although Wegener's idea of continental drift is very different from the modern theory of plate tectonics, they are related. Plate tectonics reinforce Wegener's observations, explaining how continents have moved over time.

deposition

the process in which soil, sediment, or rocks are added to a landform • sediment deposited in new location • can be part of new landform • closely linked to erosion. deposition requires that some kind of material has already been eroded and is entrained by wind, water, or ice, or is being transported by gravity

continental-continental convergence

two continents collide head-on with no subduction mountain ranges crust forced upward large earthquakes volcanoes rare

When sandstorms cause stinging eyes and fill the windows of beachside cabins with fine grains of sand, the nearby beach is left a little smaller because of erosion by:

wind

How wind shapes the landscape

wind erosion Finer particles like dust and sand, however, can become suspended in the wind and can be transported over very long distances. sand dunes wind gathers sand and dust, blowing the particles through the air. when particles encounter an obstacle momentum is broken and they settle on the ground. Larger and heavier particles settle against an obstacle; finer and lighter particles settle on the far side of an obstacle

Archean Eon

• Eon extending from the time that life originated 3.8 billion years ago, to 2.5 billion years ago. • first life • prokaryotes (possible started in late hadean eon) • photosynthesizing cyanobacteria appear ○ stromatolites

Proterozoic Eon

• Eon from 2.5 billion years ago to 570 million years ago • the atmosphere and oceans changed significantly. • eukaryotes • first multicellular life appears

Hess's contribution to theory of plate tectonics

• Harry Hess synthesized all the information and came up with the theory of seafloor spreading. Hess proposed that new ocean crust forms through volcanism at the mid-ocean ridges. Over time, the new rocks move away to either side, perpendicular to the ridge, and new lava wells up to take their place. Thus, over time, the seafloor spreads and grows. Hess suggested that convection currents in the mantle drive this motion. • In Hess's model, the continents were passengers, carried along with the seafloor by a part of the mantle that could flow and undergo convection, moving a few centimeters per year. • Seafloor spreading explained Wegener's idea of continental drift

Wegner's contribution to theory of plate tectonics

• In 1912, a German meteorologist named Alfred Wegener proposed the continents are moving and once fit together in one land mass • Wegner supported his claim with a number of lines of geological evidence, including similarities between fossils found on different continents and similar rock sequences of the same age found on different continents. Fossils also indicated that the climates had been different in the past.

Precambrian Era

• Lasted from formation of the Earth about 4.6 billion years ago to 570 million years ago • makes up about 88% of Earth's history • abundant life forms: algae, bacteria, fungi, worms, and sponges • 3 eons are Hadean, Archean, Proterozoic

Hadean Eon

• Period where earth and solar system form • earth's plates form • not many rock exists because it's mostly molten rock • atmosphere and oceans form

How gravity shapes the Earth's crust

• The downward pull of gravity causes erosion by moving water, in the form of rivers and glaciers, downhill. • directly causes erosion in the form of mass movement, in which rock and sediment move from areas of higher elevation to areas of lower elevation. • example: landslide, rockfall, mudslide, earth creep

how glaciers flow

• The force of gravity acts on the heavy but relatively low-density ice, causing it to slowly move and deform in a downhill direction. • Ice near the bottom of a glacier, close to the ground surface, flows more slowly than ice at the upper surface of a glacier due to greater friction which causes crevasses (large cracks in the ice)

how processes of erosion occur

• can be caused by liquid water, glaciers, wind, or gravity. • can occur slowly over time or rapidly during catastrophic events. • can transport material by water or air to new locations ranging from a few centimeters to thousands of kilometers away

processes that form sedimentary rocks

• formed from the compaction of particles (sand, silt, or cobbles) that have been partially buried by the weight of overlying sediments and cemented together. example: sandstone, siltstone • marine organisms extract calcium carbonate from seawater, which they use to form shells and skeletons. When they die, their shells and skeletons accumulate on the seafloor and eventually turn into rock. (fossils) example: limestone

processes that form metamorphic rocks

• formed through exposure of preexisting rock to high pressure and temperature • distort structures within a rock or to segregate and preferentially align minerals. • creates foliation (banding or layering) • or distorts or folds existing banding or structures. • examples: marble, gneiss, slate

common features that result from weathering

• weakens rock masses and wears large rocks down into smaller rocks. • rocks worn down into sand or clay. • creates and enhances cracks or joints in rocks. Once joints are present, the newly formed edges and corners will be weathered and rounded out.