Internal and External Forces How the Earth is shaped from the inside and from the outside

Internal Forces Tectonic Plates = enormous moving pieces of the earth’s lithosphere.

Internal Forces Three boundaries mark plate movements. –Divergent Boundary –Convergent Boundary –Transform Boundary

Divergent Boundary: Plates move apart, spreading horizontally

Convergent Boundary: Convergent Boundary: plates collide, causing either one plate to dive under the other or the edges of both plates to crumple.

Transform boundary: Transform boundary: plates that slide past one another.

Internal Forces A fracture in the earth’s crust is called a fault.

This is a fault line

Internal Forces Earthquakes occur when a plate grinds or slips past each another at a fault.

Internal Forces Seismographs are used to measure the intensity of an earthquake. The Richter Scale is used to determine the relative strength of an earthquake.

Seismograph machine

Internal Forces The epicenter is the point directly above the focus on the earth’s surface.

Internal Forces Earthquakes create tsunamis, which are giant waves created at the epicenter of an earthquake in the ocean. Travel 450 miles per hour, and can be as high as 200 feet.

Volcanoes When a volcano explodes, magma, gases and water from the lower crust or mantle collect underground and then pour out of a crack in the earth’s surface called a volcano. Mauna Loa, in Hawaii, the world’s largest volcano

Volcanoes The Ring of Fire is a zone around the rim of the Pacific Ocean and is the location of the vast majority of vast volcanoes.

External Forces

Weathering Weathering: physical & chemical processes that change the rock on Earth’s surface Sediment: very small pieces of rock created by weathering

Weathering

Chemical vs mechanical weathering Mechanical weathering only changes the size of the rock Chemical weathering changes the composition of the rock (it becomes a new substance) –Ex. When iron rusts

Erosion Erosion: when weathered material is moved by wind, water, or ice

Erosion

Water and Wind Erosion Water erosion can occur as water flows in a stream or river –When a river enters the ocean the sediment is deposited in a fan-like formation called a delta Windblown silt and clay sediment (loess) produces very fertile soil and is found around the world

Glacial erosion A Glacier is a large, long-lasting mass of ice that moves because of gravity Glaciation is the changing of landforms by slowly moving glaciers and the resulting erosion