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Key Terms for the Unit: • erosion • weathering, • deposition • sediment • glacier • gravity • crust • mantle • inner core • outer core • plates • tectonic plates • volcano • earthquake • fault
Tectonic Plates
Tectonic Plates
Earth's thin outer shell is broken into big pieces called tectonic plates. These plates fit together like a puzzle, but they're not stuck in one place. They are floating on Earth's mantle, a really thick layer of hot flowing rock. The flow of the mantle causes tectonic plates to move in different directions. The movement of tectonic plates along a fault can result in changes in the Earth’s surface.
Crust - The crust is the thin outer later of the Earth where we live. Well, it looks thin on the picture and it is thin relative to the other layers, but don't worry, we're not going to fall through by accident anytime soon. The crust varies from around 5km thick (in the ocean floor) to around 70km thick (on land where we live called the continental crust). The continental crust is made up of rocks that consist primarily of silica and alumina called the "sial".
Outer core - The Earth's outer core is made up of iron and nickel and is very hot (4400 to 5000+ degrees C). This is so hot that the iron and nickel metals are liquid! The outer core is very important to earth as it creates something called a magnetic field. The magnetic field the outer core creates goes way out in to space and makes a protective barrier around the earth that shields us from the sun's damaging solar wind.
Inner Core - The Earth's inner core is made up of iron and nickel, just like the outer core, however, the inner core is different. The inner core is so deep within the earth that it's under immense pressure. So much pressure that, even though it is so hot, it is solid. The inner core is the hottest part of the Earth, and, at over 5000 degrees C, is about as hot as the surface of the sun.
Mantle - The next layer of the Earth is called the mantle. The mantle is much thicker than the crust at almost 3000km deep. It's made up of slightly different silicate rocks with more magnesium and iron.
Tectonic plates - The tectonic plates are a combination of the crust and the outer mantle, also called the lithosphere. These plates move very slowly, around a couple of inches a year. Where the plates touch each other is called a fault. When the plates move and the boundaries bump up against each other it can cause an earthquake..
Identify Surface Features
Identify Surface Features
I can identify and find examples of surface features caused by constructive and/or destructive processes. (Knowledge)
I can explain the difference between weathering, erosion and deposition. (Reasoning)
I can explain how constructive and/or destructive processes impact organisms. (Reasoning)
I can collect scientific evidence to construct an argument. (Skill)
I can collect scientific evidence to construct an argument to identify surface features caused by constructive and/or destructive processes. (Product)
*** Weathering - breaks the sediment *** Erosion - takes the sediment *** Deposition - arranges or drops the sediment
Weathering
Weathering
Weathering describes a destructive process that breaks down or dissolves rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. Temperature, wind, and rain are all factors that contribute to the weathering of rocks.
Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock.
Chemical weathering changes the molecular structure of rocks and soil. Chemical weathering occurs when rocks are disintegrated by chemical reactions and occurs in moist environments. For instance, carbon dioxide from the air or soil sometimes combines with water in a process called carbonation. Materials that contain iron turn to rust in a chemical weathering process called oxidation.
Erosion
Erosion
Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. Wind carrying sand and changing the surface of a rock is an example of a destructive force. As water passes over an area, it will carry away loose soil and rocks, "carving away" at the edges of the stream bed to make it appear wider and/or deeper.
Physical erosion describes the process of human activity that breaks up rocks, changing their physical properties, such as getting smaller or smoother.
Chemical erosion describes the process of rocks changing their chemical composition as they erode.
Liquid water is the most common agent of erosion. Rainwater, rivers, and the ocean continually erode rock, sand, and soil. The wind is also a powerful force of erosion. Ice, usually in the form of glaciers or ice sheets, is a large-scale agent of erosion.
Other factors can contribute to erosion: topography, climate, and vegetation. Even the movement of the Earth itself (tectonic activity) can contribute to the disintegration and transport of sediment.
Erosion is a natural process, but human activity can make it happen more quickly. The altering of natural ecosystems for agricultural development is one of the most dramatic forces contributing to erosion.
Deposition
Deposition
Deposition is the process that follows erosion. Deposition begins when erosion stops; the moving particles fall out of the water or wind and settle on a new surface. Depositions can create Deltas. Deposition is a constructive process that creates and expands shallow land areas due to the accumulation of sediment.
The overall cause for deposition is erosion, since the particles need to be moving in order to stop. However, there has to be something that causes the erosion to stop and the deposition to begin. This transition is caused by a change in the agent of transport. Water can slow or evaporate, allowing sediment to stop being carried along. Wind can die down and release soil. Ice can melt and release its hold. Any such change begins the process of deposition.
Erosion can be a very destructive force, but together with deposition, it can also be a force of creation. These two processes are responsible for the creation of new landscapes, including hills, valleys and coastlines. Though erosion can alter an area, the affected parts are not destroyed but simply moved. Deposition allows these parts to settle elsewhere.
NOTE - Water can be constructive or destructive. Water can be a constructive force when it moves and deposits sediment to form new surface features.
Changes in Surface Features
Changes in Surface Features
I can recognize illustrated examples of surface features caused by constructive and/or destructive processes. (Knowledge)
I can illustrate and explain how weathering, erosion, and deposition work together to change earth’s surface features. (Reasoning)
I can develop simple interactive models. (Skill)
I can collect and use data to show changes in surface features cause by constructive and/or destructive processes. (Skill)
I can use interactive models to collect data related to changes in surfaces features cause by constructive and destructive processes. (Skill)
I can develop a model of surface features caused by constructive and/or destructive processes. (Product)
I can develop a model to collect data that illustrates how surface features are caused by constructive and/or destructive processes. (Product)
Constructive Processes
Constructive Processes
Stone Mountain, Georgia, is an underground ocean of molten magma. Stone Mountain was formed by magma that solidified within Earth’s crust 300-350 million years ago. Erosion removed the crust around the granite over millions of years. Stone Mountain, which is about 8 km (5 miles) around its base, is part of a huge pluton—a gigantic granite body. When you stand on top, it is hard to imagine that the mountain was once many kilometers beneath the earth’s surface. The land around the granite formation eroded away over millions of years. Also, it is hard to imagine that the mountain was a subterranean ‘ocean’ of red-hot molten rock more than 600°C (1100°F) in temperature. The magma originated when movements in the earth’s crust partly melted rocks much deeper down. Movements bent and folded the whole countryside, pushing up the Appalachian Mountains, and squeezing the magma up through the crust, to pool near the surface.
Deconstructive Processes
Deconstructive Processes
Providence Canyon, located in Atlanta, GA began forming in the early 1800s because of poor farming practices that prevailed across the nation and especially in the south. In those early days of agriculture, land was cheap, unlimited and seemingly expendable giving way to a combination of plantations, small farms, and eventually a sharecropper system that not only degraded the land but also kept farmers in debt and uneducated. Native forest cover were cleared so the land could be farmed, and no measures were taken to avoid soil erosion leading to massive loss of topsoil. Small gullies began to form and rapidly grew deeper and more extensive, until they were three to five feet deep by the 1850s. These small channels began to further concentrate runoff increasing the rate of erosion. Today, some of the gullies at Providence Canyon are 150 feet deep. The destructive force of rainwater runoff eventually created the deep gullies and ditches of Providence Canyon.
It is important to understand that one destructive force can
have a chain reaction.
Lava ejects onto the surface of the Earth through a volcano, which is a crack in the opening of the planet's crust. Lava pushes land up and hardens when it comes out of the Earth, and the resulting mountains are also called volcanoes. Shield volcanoes can shape the land for a long distance because the lava that comes out is fluid enough to travel far. Strato volcanoes are the tallest peaks formed by volcanoes. Their smaller counterparts are called cinder cones.
The multiple volcanic eruptions are a constructive force when the lava from the volcanoes cools and creates new islands. The volcanic ash that covers the area is a constructive force that deposited minerals and nutrients into the soil. The volcanic land has better quality soil and can be used for farming.
Volcanoes spew hot, dangerous gases, ash, lava, and rock that are powerfully destructive. People have died from volcanic blasts. Volcanic eruptions can result in additional threats to health, such as floods, mudslides, power outages, drinking water contamination, and wildfires. Health concerns after a volcanic eruption include infectious disease, respiratory illness, burns, injuries from falls, and vehicle accidents related to the slippery, hazy conditions caused by ash. When warnings are heeded, the chances of adverse health effects from a volcanic eruption are very low.
The Tambora caldera formed during the 1815 eruption, after 41 km3 of magma (dense rock equivalent) was expelled, leaving the 6-km-wide and 1-km-deep depression seen in this July 2019 Planet Labs satellite image mosaic (N is to the top). The current area of the caldera is approximately 34.5 km2, with erosion altering the surface and remobilizing material onto the caldera floor.
Eruption of Cleveland on 23 May 2006 as photographed from the International Space Station at an orbital altitude of approximately 400 km. The photograph shows the ash plume moving SW from the summit with N at the top and Carlisle Island to the NW.
NASA Satellite Image map of Hawaii's main islands: Hawaii, Kahoolawe, Maui, Lanai, Molokai, Oahu, Kauai, and Niihau.
A volcano can be a constructive force, that would lead to the creation of new islands, such as the Hawaiian Islands.
The Earth’s outer crust is made up of a series of tectonic plates that move over the surface of the planet. In areas where the plates come together, sometimes volcanoes will form. Volcanoes can also form in the middle of a plate, where magma rises upward until it erupts on the seafloor, at what is called a “hot spot.”
The Hawaiian Islands were formed by such a hot spot occurring in the middle of the Pacific Plate. While the hot spot itself is fixed, the plate is moving. So, as the plate moved over the hot spot, the string of islands that make up the Hawaiian Island chain were formed.
The Hawaiian Islands form an archipelago, a group of islands that extend over a vast area of the North Pacific Ocean. The archipelago is made up of 132 islands, atolls, reefs, shallow banks, shoals, and seamounts stretching over 1,500 miles from the island of Hawaii in the southeast to Kure Atoll in the northwest.
Earthquakes
Earthquakes
Earthquakes are caused by movement of crustal plates in the Earth's surface. Plates might grind against, or slide above or beneath one another. When the rocks break, they cause seismic waves to ripple away from the breaking point. Earthquakes emerge as a rapid shaking of the Earth, which can sometimes be felt by living organisms. The resulting force on the Earth's land includes faults, landslides, rifts and tsunamis. They can also cause damage to buildings and roads.
The Ring of Fire is a region around much of the rim of the Pacific Ocean where many volcanic eruptions and earthquakes occur.
Tsunami
Tsunami
A tsunami is a series of ocean waves caused by any large and sudden disturbance of the sea surface. Tsunamis can be generated by landslides, volcanic eruptions, or even meteorite impacts in the ocean. But they are most often caused by an earthquake where there’s a sudden displacement of the ocean floor.
When that happens, there’s a transfer of energy from the seafloor to the ocean, causing waves on the surface to radiate outward in all directions
A hurricane is a large rotating storm with high speed winds that forms over warm waters in tropical areas. Hurricanes have sustained winds of at least 74 miles per hour and an area of low air pressure in the center called the eye. The scientific name for a hurricane is a tropical cyclone. Tropical cyclones go by different names in different places. In North America and the Caribbean they are called "hurricanes", in the Indian Ocean they are called "cyclones", and in Southeast Asia they are called "typhoons."
Hurricanes form over the warm ocean water of the tropics. When warm moist air over the water rises, it is replaced by cooler air. The cooler air will then warm and start to rise. This cycle causes huge storm clouds to form. These storm clouds will begin to rotate with the spin of the Earth forming an organized system. If there is enough warm water, the cycle will continue and the storm clouds and wind speeds will grow causing a hurricane to form.
Canyon
Canyon
Canyons are created by the destructive process of constant erosion by a river over millions of years. When a river cuts through resistant rocks to form a steep-walled, deep V-shaped valley, it results in the formation of a canyon. Canyons usually occur in a river’s upper course where the river has a powerful and swift current that allows the river to dig deep into the valley floor.
The erosion of plateaus or mountains formed by a river cutting through the rocks over geologic timescales results in the formation of a canyon. Rivers have a natural tendency to erode the surfaces lying underneath its water level to allow for a smoother flow of water. Usually, the river keeps cutting through the underlying rock till the river reaches a baseline elevation which is the same elevation as the water body into which the river drains.
The wind and water from rivers erode away the less resistant rocks like shale from the river bed and banks. Frost wedging in rivers forming canyons at higher altitudes also assist the erosion process. Here water enters the cracks and crevices of rocks and freezes during periods of low temperature. The ice crystals formed between rocks push the rocks apart and results in chunks of rocks breaking down. The harder rock strata that are usually made of granite or sandstone forms the walls of the canyon as it is resistant to weathering processes.
Valley
Valley
The movement of water across Earth’s surface can erode the land to create a valley. A valley is an extended depression in the Earth's surface that is usually bounded by hills or mountains and is normally occupied by a river or stream. Since valleys are usually occupied by a river, they can also slope down to an outlet which can be another river, a lake or the ocean.
Valleys are one of the most common landforms on the Earth and they are formed through erosion or the gradual wearing down of the land by wind and water. In river valleys, for example, the river acts as an erosional agent by grinding down the rock or soil and creating a valley. The shape of valleys varies but they are typically steep-sided canyons or broad plains, however, their form depends on what is eroding it, the slope of the land, the type of rock or soil and the amount of time the land has been eroded.
There are three common types of valleys which include V-shaped valleys, U-shaped valleys, and flat-floored valleys.
Barrier Islands
Barrier Islands
Barrier islands form as waves repeatedly deposit sediment parallel to the shoreline. The shoreline of the barrier island has been altered over time due to destructive forces. As wind and waves shift according to weather patterns and local geographic features, these islands constantly move, erode, and grow. They can even disappear entirely.
They are generally separated from the mainland by tidal creeks, bays, and lagoons. Beaches and sand dune systems form on the side of the island facing the ocean; the side facing the shore often contains marshes, tidal flats, and maritime forests. These areas are important habitat for seabirds, fish and shellfish, and nesting sea turtles.
Sand Dunes
Sand Dunes
Sand dunes are created when wind deposits sand on top of each other until a small mound starts to form. Once that first mound forms, sand piles up on the windward side more and more until the edge of the dune collapses under its own weight. The collapse begins when the angle of the dune becomes too large to support the weight. This is called the angle of repose and is usually around 30-34o, but depends on factors such as grain size, wind speed, and roundedness of the individual grains. As these dunes collapse they move in the same direction as the wind, and if there is no wind moving in the opposite direction or any obstacles in its path, barchan dunes are formed.
Delta
Delta
Deltas are surface features caused by constructive processes and are formed when rivers deposit sediment and build up layers of topset beds. Deposition is a constructive force that uses the flow of the water in the river to move sediment to the mouth of the river. Where rivers provide large quantities of sediment to the shore, estuaries are filled and river sediments (sand, clay, and silt) are discharged directly into the ocean. If the rate of sediment supply exceeds the rate of sediment removal by waves and tidal currents, a buildup of sediment occurs at river mouths. These deposits, which commonly assume triangular shapes in planar view, are termed deltas because they resemble the Greek capital letter delta (Δ).
Mississippi River Delta
Mississippi River Delta
The surface feature is a delta that was formed by a constructive process when the flowing water of the Mississippi River deposited sediment at the mouth of river.
Beach Erosion
Beach Erosion
High waves have inundated the beach and are eroding the dune in this view of Narrabeen beach, Australia.
Beach erosion is one of the most common impacts of extreme storm events, as elevated wave energy, in combination with winds, currents and elevated water levels drive sediment offshore from shallow to deeper waters.
Jetty
Jetty
A jetty is a long, narrow structure that protects a coastline from the currents and tides. They are a wall-like structure that sticks out in the ocean to prevent sand from being carried away. Jetties are usually made of wood, earth, stone, or concrete. They stretch from the shore into the water. Jetties protect the shoreline of a body of water by acting as a barrier against erosion from currents, tides, and waves.
Levee / Dike
Levee / Dike
Embankments of stone, cement, or soil that hold back water or prevent the overflow of a river from dry land are called levees or dikes. Levees protect land that is normally dry but that may be flooded when rain or melting snow raises the water level in a body of water, such as a river. Dikes protect land that would naturally be underwater most of the time. Levees and dikes look alike, and sometimes the terms levee and dike are used interchangeably.
Levees need to be able to absorb water, so using an absorbent material is important when building new levees.
Dam
Dam
A dam is a large wall or barrier that obstructs or stops the flow of water, forming a reservoir or a lake. Most dams have a section called a spillway or weir over which, or through which, water flows, either sometimes or always. Dams generally serve the primary purpose of retaining water.
Storm Drain
Storm Drain
Flooding is influenced by the amount of precipitation that falls within a certain period. Storm drains are human interventions used to drain heavy rainfall flooding waters from roads and neighborhoods.
Landslide
Landslide
A landslide is a large amount of earth, rock, and other material that moves down a steep slope. Landslides happen when a layer of earth or rocks separates from the layer below it. The force of gravity pulls the loose layer downward.
Landslides can be highly destructive. They can bury or sweep away everything in their path. They can block rivers or cover entire towns.
A landslide needs a steep slope to get its start. Rain, wind, waves, and other natural processes can wear away the surface of a slope. This wearing away, or erosion, can make a slope too steep to support the rocks and earth on top. Erosion can also loosen or weaken the material on a slope. This makes it easier for gravity to pull the material down the slope.
Besides erosion, other forces can lead to landslides. Rainstorms, melting snow, and earthquakes can weaken the material on a slope. Earthquakes, volcanoes, and the use of construction equipment or explosives can force material down a slope.
Rockfalls, mudflows, and avalanches are similar to landslides. A rockfall involves large rocks falling from the top of a slope or a cliff. A mudflow is a thick stream of mud and other material that moves quickly downward. An avalanche is the sudden downward movement of snow or other material.
Glacier
Glacier
Glaciers are a massive body of ice that moves slowly across land. Glaciers can be hundreds or thousands of meters (yards) deep. They form in places where snowfall does not completely melt each year. Over time, the weight of the snow piling up compresses the snow below, turning it to ice. At the very bottom, the ice becomes viscous, meaning it is able to flow and move.
Such huge masses of ice grinding across the land leave their mark. They can carry or push soil, rocks and big boulders. They can erode the land and gouge deep valleys. Dents and divots left by glaciers have filled with water to form lakes.
Island
Island
Islands are areas of land that are not connected to a continent and are surrounded by water. Small islands are sometimes called cays, keys, or islets. A group of islands is often called an archipelago. There are two main type of islands; continental islands and oceanic islands. Continental islands are part of a continental shelf. One example of this is Great Britain is an island that sits on the continental shelf of Europe. Oceanic islands are islands that don't sit on a continental shelf. Many oceanic islands are formed by undersea volcanoes like Hawaii in the Pacific Ocean.
Technology Used to Limit Impact
Technology Used to Limit Impact
I can identify how technology is used to limit the impact of constructive and destructive processes. (Knowledge)
I can identify how technology is used to predict the impact of constructive and destructive processes. (Knowledge)
I can ask questions to gather information to show how technology is used to limit the impact of constructive and destructive processes. (Reasoning)
I can ask questions to obtain information on how technology is used to predict the impact of constructive and destructive processes. (Reasoning)
Seismograph - instruments used to record the motion of the ground during an earthquake. They are installed in the ground throughout the world and operated as part of a seismographic network. The first seismograph was developed in 1890. A seismograph is securely mounted onto the surface of the earth so that when the earth shakes, the entire unit shakes with it EXCEPT for the mass on the spring, which has inertia and remains in the same place. As the seismograph shakes under the mass, the recording device on the mass records the relative motion between itself and the rest of the instrument, thus recording the ground motion. In reality, these mechanisms are no longer manual, but instead work by measuring electronic changes produced by the motion of the ground with respect to the mass.
Infrared Satellite Imagery - Infrared satellite pictures show clouds in both day and night. Instead of using sunlight to reflect off of clouds, the clouds are identified by satellite sensors that measure heat radiating off of them. The sensors also measure heat radiating off the surface of the earth. Clouds will be colder than land and water, so they are easily identified. Infrared imagery is useful for determining thunderstorm intensity. Strong to severe thunderstorms will normally have very cold tops. Infrared imagery can also be used for identifying fog and low clouds. The fog product combines two different infrared channels to see fog and low clouds at night, which show up as dark areas on the imagery.
GIS Mapping - A Geographic Information System (GIS) is a computer system that analyzes and displays geographically referenced information. It uses data that is attached to a unique location. Most of the information we have about our world contains a location reference: Where are USGS streamgages located? Where was a rock sample collected? Exactly where are all of a city's fire hydrants? If, for example, a rare plant is observed in three different places, GIS analysis might show that the plants are all on north-facing slopes that are above an elevation of 1,000 feet and that get more than ten inches of rain per year. GIS maps can then display all locations in the area that have similar conditions, so researchers know where to look for more of the rare plants. By knowing the geographic location of farms using a specific fertilizer, GIS analysis of farm locations, stream locations, elevations, and rainfall will show which streams are likely to carry that fertilizer downstream. These are just a few examples of the many uses of GIS in earth sciences, biology, resource management, and many other fields.
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