The Geosphere Ch. 3 sec. 1B

Plate Tectonics Tectonic Plates – pieces of the lithosphere –Glide across the underlying asthenosphere –Continents move along these plates

Continental Drift

Plate Tectonics Pacific plate North American plate South American plate African plate Eurasian plate Antarctic plate

Plate Boundaries Geologic activity usually occurs between tectonic plates

Plate Boundaries Diverging – plates move apart from one another –New ocean floor

Plate Boundaries convergent- plates move toward one another –Mountain ranges

Plate Boundaries Subduction – slip past one another –volcanoes

Volcanoes Mountain built from magma (melted rock) that rises from the Earth’s interior to its surface

Volcanoes Often located near plate boundaries (colliding or seperating)

Volcanoes Can occur in land or sea –Sea, usually turn into islands

Volcanoes Erupts when pressure of magma inside becomes so great that it blows open the solid surface

Volcanoes Some may always flow so that pressure never builds up and they never erupt

Volcanoes Negatives –Clouds of hot ash, dust and gas –Ash can mix with water and create a mud flow –Ash can cause buildings to collapse, bury crops

Volcanoes Can change Earth’s climate –Mt. St. Helens Ash and sulfuric gas reach upper atmosphere Reduce sunlight (temp decrease)

Earthquakes Fault (Transform)= break in the Earth’s crust along which blocks of the crust slide relative to one another –Creates vibrations

Earthquakes Earthquakes = vibrations due to slippage of fault plates –Occur all the time but we don’t necessarily feel them

Earthquakes Richter scale – used to quantify the amount of energy released from earthquake Richter scale no.No. of earthquakes per year Typical effects of this magnitude < Detected only by seismometers Just about noticeable indoors Most people notice them, windows rattle Everyone notices them, dishes may break, open doors swing Slight damage to buildings, plaster cracks, bricks fall Much damage to buildings: chimneys fall, houses move on foundations Serious damage: bridges twist, walls fracture, buildings may collapse Great damage, most buildings collapse. > 8.0One every 5 to 10 years Total damage, surface waves seen, objects thrown in the air. 9.0 — Causes complete devastation and large-scale loss of life. 8.0 — Very few buildings stay up. Bridges fall down. Underground pipes burst. Railroad rails bend. Large rocks move. Smaller objects are tossed into the air. Some objects are swallowed up by the earth. 7.0 — It is hard to keep your balance. The ground cracks. Roads shake. Weak buildings fall down. Other buildings are badly damaged. 6.0 — Pictures can fall off walls. Furniture moves. In some buildings, walls may crack. 5.0 — If you are in a car, it may rock. Glasses and dishes may rattle. Windows may break. 4.0 — Buildings shake a little. It feels like a truck is passing by your house. 3.0 — You may notice this quake if you are sitting still, or upstairs in a house. A hanging object, like a model airplane, may swing. 2.0 — Trees sway. Small ponds ripple. Doors swing slowly. But you can't tell an earthquake is to blame. 1.0 — Earthquakes this small happen below ground. You can't feel them.

Earthquake Richter scale measures magnitude –Smallest 2.0 –Largest 9.5

Earthquake Most take place at or near plate boundaries –San Andres Fault (between North American and Pacific plate)

Earthquake Can’t predict them but scientist know where they may occur

Erosion The removal and transport of surface material –Change of rock layers due to wind and water

Erosion Wears down rocks and makes them smoother over time –Older the mountain range the more erosion is should have –Applachain Mtn. are older than Rocky Mtns

Water Erosion Rivers and ocean

Water Erosion Ocean waves erode coastlines

Water Erosion Rivers can carve deep gorges into landscape

Wind Erosion Plants adapt with roots to hold onto soil Loose soil, plants blow away

Wind Erosion Soft rocks (sandstone) –Erode easier

Wind Erosion Hard rocks (granite) –Longer to erode