Earth’s Changing Surface Chapter 7

Weather and Erosion are major forces that shape the Earth's surface. Example: The Grand Canyon was formed by the Colorado River running through it. Weather and Erosion are major forces that shape the Earth's surface.

Surface processes the process of erosion and weathering affecting the geosphere a process caused by nature rather than by the deliberate act of human beings

What is weathering? Weathering = The breaking down of rocks into smaller pieces. 1. Physical 2. Chemical

So what is Erosion? Erosion = The movement of weathered rock by wind, rain, glaciers, and gravity.

Types of Weathering Mechanical / Physical Chemical Rocks are physically broken into smaller pieces (larger pieces become smaller pieces of the same rock Rock is chemically changed like rusting or dissolving away

5 Ways of Mechanical Weathering: 1. Release of Pressure 2. Freezing & Thawing 3. Animal Actions 4. Plant Growth 5. Abrasion

Release of Pressure As the surface of a rock is eroded, the rock begins to release pressure Causes top layers of the rock to crack and flake off Release of pressure causes rock to crack like an egg shell

Freezing and Thawing When water in the cracks of rocks freezes it expands This causes the crack to get bigger The ice melts and refreezes over and over again This action breaks the rock apart

Animal Actions Animals dig (burrow) through the ground to make their homes This loosens the soil and breaks rocks apart

Plant Growth Plant roots can grow into cracks in the rock When the plant grows the roots thicken widening the crack in the rock

Abrasion Sand and other rock particles in the wind, water, or ice can wear away rock surfaces Just like sandblasting or sandpaper on wood

= The process that breaks down the surface of rock by chemical changes Chemical Weathering = The process that breaks down the surface of rock by chemical changes

5 Causes of Chemical Weathering Water Oxygen Carbon Dioxide Living Organisms Acid Rain

Water Water dissolves rock Water is the MOST important cause of chemical weathering

Oxygen Oxygen + Water + Iron = Rust This chemical reaction is called Oxidation Rocks will become crumbly, soft, and appear reddish-brown

Carbon Dioxide Carbon Dioxide (CO2) + water = Carbonic Acid Carbonic Acid weathers softer rock like limestone and marble as it seeps into spaces in rock Examples: sinkholes, caves

Living Organisms The roots of plants make a weak acid that slowly dissolves rocks around the plant

Acid Rain Acid rain causes rocks to weather very rapidly Pollution causes acid rain

Horizons = layers of soil which develop over time A = Topsoil B = Subsoil or larger rock particles C = Regolith of weathered rock D = solid rock

7. 2 Earth’s Surface

Deposition particles of rock are laid down in layers Heavier particles are dropped first and then covered by finer material Layers of sediment build up over time

Drainage Basin any area of land where precipitation collects and drains off into a body of water.

River Delta = a landform that forms from deposition of sediment The sediment is carried by a river but does not have the energy/speed to carry it all away so is deposited at the mouth of the river This occurs where a river enters a larger body of water and cannot carry away the sediment

Sinkhole  is a depression in the ground that forms when the rock beneath the surface collapses

Longshore Current is an ocean current that moves parallel to shore It is caused by large waves sweeping into the shoreline at an angle and pushing water down the length of the beach in 1 direction

Glacier Large area of ice on land formed by the accumulation and compaction of snow on mountains or near the poles

a mass of rocks and sediment carried down and deposited by a glacier Moraines a mass of rocks and sediment carried down and deposited by a glacier

Plateau is an area of a land higher than surrounding area consisting of relatively flat land that is raised significantly above the surrounding area often with steep slopes

7.3 Development of Features

Active Margin Oceanic crust goes under the continental crust forming a trench (dip) is found on the leading edge of the continent where it pushes into an oceanic plate sites of tectonic activity like earthquakes and volcanoes

Passive Margin Begins at divergent plate boundaries As the plates move apart oceanic crust is added   Continental rifting creates new ocean basins Page 431

Isostatic Equilibrium Huge plates of crust and upper mantle (lithosphere) “float” on more dense, plastically flowing rocks of the asthenosphere The balance is called isostatic equilibrium Isostatic = restored with negative feedback Equilibrium = forces in balance

Is the upward motion caused from convergent plates lifting large areas Uplift Is the upward motion caused from convergent plates lifting large areas

the sinking of the Earth's crust on a large scale Subsidence the sinking of the Earth's crust on a large scale