The GeosphereThe Geosphere

Ch. 3 sec. 1BCh. 3 sec. 1B

Plate TectonicsPlate Tectonics

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

Continental DriftContinental Drift

Plate TectonicsPlate Tectonics

• Pacific plate

• North American plate

• South American plate

• African plate

• Eurasian plate

• Antarctic plate

Plate BoundariesPlate Boundaries

• Geologic activity usually occurs between tectonic plates

Plate BoundariesPlate Boundaries

• Diverging – plates move apart from one another– New ocean floor

Plate BoundariesPlate Boundaries

• convergent- plates move toward one another– Mountain ranges

Plate BoundariesPlate Boundaries

• Subduction – slip past one another– volcanoes

VolcanoesVolcanoes

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

VolcanoesVolcanoes

• Often located near plate boundaries (colliding or seperating)

VolcanoesVolcanoes

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

VolcanoesVolcanoes

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

VolcanoesVolcanoes

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

VolcanoesVolcanoes

• 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

VolcanoesVolcanoes

• Can change Earth’s climate– Mt. St. Helens

• Ash and sulfuric gas reach upper atmosphere• Reduce sunlight (temp decrease)

EarthquakesEarthquakes

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

EarthquakesEarthquakes

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

feel them

EarthquakesEarthquakes

• Richter scale – used to quantify the amount of energy released from earthquake

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.

EarthquakeEarthquake

• Richter scale measures magnitude– Smallest 2.0– Largest 9.5

EarthquakeEarthquake

• Most take place at or near plate boundaries– San Andres Fault (between North American

and Pacific plate)

EarthquakeEarthquake

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

ErosionErosion

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

ErosionErosion

• 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 ErosionWater Erosion

• Rivers and ocean

Water ErosionWater Erosion

• Ocean waves erode coastlines

Water ErosionWater Erosion

• Rivers can carve deep gorges into landscape

Wind ErosionWind Erosion

• Plants adapt with roots to hold onto soil

• Loose soil, plants blow away

Wind ErosionWind Erosion

• Soft rocks (sandstone)– Erode easier

Wind ErosionWind Erosion

• Hard rocks (granite)– Longer to erode