The Earth Notes

Water, Land, and Air About 70% of our planet’s surface is water Oceans, lakes, rivers, and other bodies of water make up the hydrosphere Land makes up the part of the earth called the lithosphere; it also includes the ocean basins (land beneath the oceans) The air we breathe is part of the atmosphere ~ 6,000 miles above the planet’s surface Biosphere: part of earth that supports life

Landforms 7 continents Continental Shelf – part of a continent that extends underwater

The Earth’s Interior Inner Core – about 4000 miles below the surface of the Earth Outer Core – 1400 mi. thick, temperature reaches 8500°F

Earth’s Interior (con’t) Mantle: layer of hot, dense rock – MAGMA Crust: rocky shell forming Earth’s surface; crust is broken into slabs of rock called plates Plates float on a melted layer in the upper mantle; carry the earth’s oceans and continents

Plate Movement Continental Drift: the theory that the continents were once joined and then slowly drifted apart Pangea: gigantic super continent which eventually broke apart Plate movement creates oceans and mountain ranges

Volcanic Eruptions Ring of Fire – on of the most earthquake-prone areas on the planet; also volcanoes Volcanoes are often along plate boundaries; magma splits the earth’s surface as plates collide

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

Converging/Collision Zone They 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 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 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.

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.

Important forces in CHEMICAL WEATHERING are moisture and carbon dioxide. Through this process caves are created. 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. Most common agents of erosion are water, wind and glaciers.

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

Sediment creates new landforms such as – FLOODPLAINS –DELTAS formed at the mouth of a river

WIND AND EROSION 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? LOESS – windblown deposits of mineral-rich dust

GLACIERS CAUSE EROSION? GLACIERS are slow moving sheets of ice that are formed over many years. How do they cause erosion? The movement cuts though land creating lakes. They melt away and then rebuild again over thousand of years.