Tectonic Terms: Key Terms

Tectonic Terms: Key Terms.

Geology: The study of the physical earth and the processes that create it, shape it, and destroy it.

Seismologist: Scientists who study earthquakes and the movement of the earth’s crust

Tectonics: Related to the study of the internal forces under the crust which deform (change) the earth’s
crust.

Continental drift: Theory by Alfred Wegener that said that at one time all the earth’s continents were one piece called
Pangea.
-The continental Plates then drifted apart 300 mil. years ago to their present locations
- Problem with his theory: He could not explain “how “ the plates moved.

Wegener’s Proofs for the Theory of Continental Drift:
1. - Jigsaw Fit: He saw that many continents could fit together:
-India and Africa and South America and Africa)

2. Fossil Evidence: Fossils from the same plants and animals found on different continents

3. The Same Mountain Ranges: Mountains in either side of the Atlantic Ocean have similar
structure and mineral composition.

4. Glaciers/Ice Sheets evidence: India, Africa, Australia and South America all show evidence of
being covered by giant glaciers and Ice Sheets.

Pangaea: Refers to the super continent that existed 300 million years ago. Pangaea means “all land”.

Plate Tectonics: Theory developed by J. Tuzzo Wilson discovered that plates move by convection currents

Convection Currents: Heat the magma in the mantle which rises to the surface, creating a current.
They are the driving force that moves the earth’s crust.

Earth’s Layers: composed of 4 main layers: crust, mantle, outer core, inner core

Trench: When two plates collide, one descends under the other, creating a trench (long, deep, valley)

Ridge: When two plates move apart, magma seeps up and fills the crack, creating a Ridge (long hill)

Erosion: the wearing down of mountains or rocks in general

Agents of Erosion: Wind, water (rain, running water) and ice all erode rock.
- Wind picks up rock particles and smashes them against others
- Water dissolves minerals in the rock or wears it away with wave action (moving water)
- Ice takes up more space than water. The Freeze/Thaw cycle breaks up rocks by constantly
putting pressure on the cracks in the rocks. Glaciers wear away mountains

Mountain Building Forces:

- Folding: Plates come together and the pressure forces the crust to fold into mountains

- Faulting: When the earth cracks open at plate boundaries and the plates move together or apart.

- Volcanism: The lava that comes out of the volcano creates new rock and mountains.

Divergent Boundaries: Fault lines where the continents meet and are exerting pressure away from each other often creating rift valleys (St, Lawrence River valley) or volcanic regions (Pacific Rim of fire)

Convergent Boundaries: Fault lines where the continents meet and are exerting pressure towards each other, creating folded or block mountains.

Transform Boundaries: Fault lines where the continents meet slide by each other, San Andreas Fault in California.