Earth Notes Chapter 2 ~ Section 2 Forces of Change

The Earth’s Interior Inner Core – about 4,000 miles below the surface of the Earth Inner Core – about 4,000 miles below the surface of the Earth Outer Core – 1,400 miles thick, temperature reaches 8500°F Outer Core – 1,400 miles thick, temperature reaches 8500°F

Earth’s Interior (con’t) Mantle: layer of hot, dense rock – MAGMA Mantle: layer of hot, dense rock – MAGMA

Earth’s Interior (con’t) Crust: rocky shell forming Earth’s surface. Crust: rocky shell forming Earth’s surface. The crust is broken into slabs of rock called plates. The crust is broken into slabs of rock called plates. Natural forces interact with the crust, creating landforms on the surface of the earth. Natural forces interact with the crust, creating landforms on the surface of the earth. Below the oceans, the crust is about 5 miles thick. Below the continents it averages 22 miles in thickness. Below the oceans, the crust is about 5 miles thick. Below the continents it averages 22 miles in thickness.

Earth’s Interior (con’t) Plates - float on a melted layer in the upper mantle Plates - float on a melted layer in the upper mantle - carry the earth’s oceans and continents - carry the earth’s oceans and continents

Internal Forces of Change

 The lithosphere — the earth’s crust and upper layer of the mantle — is broken into a number of large, moving plates. The Plate Tectonic Theory

 The plates slide very slowly over a hot, pliable layer of mantle.   The earth’s oceans and continents ride atop of the plates.   It’s along the plate boundaries that most earthquakes and volcanoes occur due to friction and pressure that produces heat. The Plate Tectonic Theory

Plate Movement Plate movement: creates oceans and mountain ranges

Plate Movement Continental Drift: the theory that the continents were once joined and then slowly drifted apart Continental Drift: the theory that the continents were once joined and then slowly drifted apart

Plate Movement Pangaea: gigantic super continent which eventually broke apart

Ring of Fire A A circle of volcanic mountains surrounding the Pacific Ocean It is one of the most earthquake-prone & volcano-prone areas on the planet. It is one of the most earthquake-prone & volcano-prone areas on the planet. Hot Spots Hot Spots are hot regions deep within the mantle that produce magma, which rises to the surface. Volcanic island chains form as oceanic plates drift over the hot spot. Example: Hawaiian Islands.

Volcanoes Form when magma inside the earth breaks through the crust. Lava flows and may produce a large, cone-shaped mountain Form when magma inside the earth breaks through the crust. Lava flows and may produce a large, cone-shaped mountain They often form along plate boundaries They often form along plate boundaries Magma splits the earth’s surface when plates collide Magma splits the earth’s surface when plates collide

Fault—a break in the earth’s crust. Movement along a fault can send out shock waves, causing an earthquake.

San Andreas Fault

A devastating fire followed the 1906 earthquake in San Francisco

The San Fernando earthquake of 1971 collapsed freeway overpasses in southern California

Converging/Collision Zone Plates collide and push slowly against each other and form a collision or converging zone. Plates collide and push slowly against each other and form a collision or converging zone. If 2 oceanic plates collide, 1 slides under the other. Islands often form this way. If 2 oceanic plates collide, 1 slides under the other. Islands often form this way. If 2 continental plates collide, mountains are formed. Example: Himalayas If 2 continental plates collide, mountains are formed. Example: Himalayas

Continental Crush / Collide

Spreading Zone Plates pull away from each other and form a spreading zone. These areas are likely to have earthquakes, volcanoes, and rift valleys (a large split along the crest of a mountain).

Spreading Zone

Subduction They meet, or CONVERGE and form a subduction zone. *If an oceanic plate collides with a continental plate, the heavier oceanic plate will slide under the lighter, continental plate. This results in volcanic mountain building and earthquakes.

Subduction

External Forces of Change

External Forces What other forces can create landforms? What other forces can create landforms? Weathering – a process that breaks down rock at or near the surface into smaller pieces. This is a VERY slow process – thousands to millions of years. Weathering – a process that breaks down rock at or near the surface into smaller pieces. This is a VERY slow process – thousands to millions of years.

Mechanical Weathering occurs when rock freezes – it can cause Frost Wedging, a crack in the rock caused by freezing. Mechanical Weathering occurs when rock freezes – it can cause Frost Wedging, a crack in the rock caused by freezing. Chemical Weathering – alters the rock’s chemical makeup by changing the minerals. This can actually change one kind of rock into another. Chemical Weathering – alters the rock’s chemical makeup by changing the minerals. This can actually change one kind of rock into another.

Important forces in Chemical Weathering are moisture and carbon dioxide. Important forces in Chemical Weathering are moisture and carbon dioxide. Through this process caves are created. Through this process caves are created. Acid Rain causes another type of chemical weathering that destroys forests, pollutes water and kills wildlife. Acid Rain causes another type of chemical weathering that destroys forests, pollutes water and kills wildlife.

EROSION Erosion is the movement of weathered materials including gravel, soil and sand. Erosion is the movement of weathered materials including gravel, soil and sand. The most common agents of erosion are water, wind and glaciers. The most common agents of erosion are water, wind and glaciers.

Erosion Erosion due to wave pounding at Venus Bay, South Australia.

WATER AND EROSION Moving Water (rain, rivers, streams and oceans) is the greatest agent of erosion. Moving Water (rain, rivers, streams and oceans) is the greatest agent of erosion. Sediment – small particles of soil, sand, and gravel - are carried by the moving water and works like sandpaper to grind away rocks. Sediment – small particles of soil, sand, and gravel - are carried by the moving water and works like sandpaper to grind away rocks.

Sediment Sediment from the River Rhône flowing into Lake Geneva.

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Sediment creates new landforms such as floodplains & deltas. Floodplains Deltas form at the mouth of a river

Wind Erosion The second major cause of erosion is wind, especially where there is little water and few plants. The second major cause of erosion is wind, especially where there is little water and few plants. Wind Erosion can devastate one area while benefiting another – HOW? Wind Erosion can devastate one area while benefiting another – HOW? Loess – windblown deposits of mineral-rich dust Loess – windblown deposits of mineral-rich dust

GLACIERS CAUSE EROSION? Glaciers are slow moving sheets of ice that are formed over many years.

GLACIERS How do they cause erosion? How do they cause erosion? The movement cuts though land creating lakes. The movement cuts though land creating lakes. They melt away and then rebuild again over thousand of years. They melt away and then rebuild again over thousand of years.