2. I. Plate Tectonics
A. The Earth Moves
1. Tectonic plates are massive, moving
pieces of Earth’s lithosphere.
2. Plates ride above circulating, heated
3. Geographers study plate movements to
a. how the earth is reshaped.
b. how earthquakes and volcanoes are
3. B. Plate Movement
1. Plates move in one of four ways:
a. by spreading, or moving apart.
b. subduction, or diving under another
c. collision, or crashing together.
d. sliding past each other in a shearing
4. 2. Movement of plates effects surface of
3. Saudi Arabia–Egypt’s plates are
spreading apart, widening Red Sea.
4. India’s plate is crashing into Asian
continent, building up Himalayas.
5. Three types of boundaries mark plate
a. divergent boundary
b. convergent boundary
c. transform boundary
5. D. Folds and Faults
1. Two plates meeting can cause folding,
cracking of rock.
2. Fault occurs when pressure causes rock to
fracture, or crack.
3. Fault line is place where plates move past each
6. II. Earthquakes
A. The Earth Trembles
1. An earthquake occurs when plates grind or slip at a fault
2. A seismograph detects earthquakes and measures the waves
B. Earthquake Locations
1. Location in the earth where an earthquake begins is called
the focus .
2. Epicenter—the point directly above focus on the earth’s
3. Nearly 95% of earthquakes occur at tectonic plate boundaries
7. C. Earthquake Damage
1. Earthquakes release energy in the form of motion,
b. land displacement
c. fires (broken gas lines)
d. collapsed buildings
2. Richter Scale—numeric scale showing relative
strength of earthquake.
1. Tsunami, a giant ocean wave, begins at epicenter
of an earthquake:
a. travels at up to 450 mph.
b. waves of 50–100 ft. or higher.
8. III. Volcanoes
A. The Explosive Earth
1. Volcano—underground materials pour from crack in
the earth’s surface.
2. Most volcanoes occur at tectonic plate boundaries.
B. Volcanic Action
1. Eruption—lava, gases, ash, dust, explode from vent in
2. Lava—magma that has reached the earth’s surface;
may create landform.
9. C. Ring of Fire
1. Ring of Fire—zone around rim of Pacific
a. meeting point of eight tectonic plates.
b. vast majority of the earth’s active volcanoes
2. ―Hot spots‖ are where magma rises to surface
3. Hot springs, geysers indicate high
temperatures in earth’s crust.
4. Some volcanic action is useful:
a. volcanic ash produces fertile soil.
b. hot springs are tapped for heat, energy.