Geology: Continental Drift and Seafloor Spreading

Study Notes

Theory proposed by Alfred Wegener in 1912
Suggests that continents have moved over time and were once joined together in a single supercontinent, Pangaea
Evidence:
- Fit of the continents like a jigsaw puzzle
- Similarity of rock formations and fossils on different continents
- Same age and type of rocks on different continents

Theory that explains the creation of new oceanic crust at mid-ocean ridges
Process:
1. Magma rises from the Earth's mantle to the surface
2. Magma cools and solidifies, forming new oceanic crust
3. New crust is pushed away from the ridge by the continuous flow of magma
4. Older crust is destroyed at deep-sea trenches
Evidence:
- Magnetic striping: alternating magnetic polarities on either side of mid-ocean ridges
- Age of the rocks: youngest rocks at the ridges, increasing age with distance from the ridge
- Mid-ocean ridges: topographic features where new crust is being created

Volcanic regions where magma is able to rise to the surface through the Earth's crust
Characterized by:
- Volcanic activity
- Formation of shield volcanoes
- Creation of volcanic islands
Evidence:
- Hawaii-Emperor seamount chain: a chain of volcanic islands and seamounts formed by the movement of the Pacific plate over a hotspot
- Yellowstone hotspot: a region of volcanic activity in the western United States formed by the movement of the North American plate over a hotspot

Caused by the movement of tectonic plates
Types:
- Shallow focus: occur at the boundary between two plates
- Deep focus: occur within a subducting plate
Characteristics:
- Release of energy: seismic waves
- Epicenter: location on the Earth's surface directly above the earthquake
- Focal depth: distance from the Earth's surface to the earthquake

Result of the collision of two tectonic plates
Processes:
- Continental collision: two continental plates collide, resulting in the formation of mountains
- Oceanic-continental convergence: an oceanic plate collides with a continental plate, resulting in the formation of mountains
- Arc-continent collision: an oceanic plate collides with a continental plate, resulting in the formation of mountains
Examples:
- Himalayan mountain range: formed by the collision of the Indian plate with the Eurasian plate
- Andes mountain range: formed by the subduction of the Nazca plate under the South American plate

Alfred Wegener proposed the theory in 1912, suggesting continents have moved over time and were once joined in Pangaea
Evidence includes the continents' jigsaw-like fit, similar rock formations and fossils across different continents, and same-age rocks on multiple continents

Theory explaining the creation of new oceanic crust at mid-ocean ridges
Process involves:
- Magma rising from the Earth's mantle to the surface
- Magma cooling and solidifying to form new oceanic crust
- New crust being pushed away from the ridge by continuous magma flow
- Older crust being destroyed at deep-sea trenches
Evidence includes magnetic striping, age of rocks (youngest at ridges, increasing with distance), and mid-ocean ridges as topographic features of new crust creation

Volcanic regions where magma rises to the surface through the Earth's crust
Characteristics include volcanic activity, shield volcano formation, and creation of volcanic islands
Evidence includes the Hawaii-Emperor seamount chain and Yellowstone hotspot, both formed by plate movement over fixed hotspots

Caused by tectonic plate movement
Types include shallow focus (at plate boundaries) and deep focus (within subducting plates)
Characteristics include energy release in seismic waves, epicenter location on the Earth's surface, and focal depth (distance from surface to earthquake)

Result of tectonic plate collision
Processes include:
- Continental collision: two continental plates collide, forming mountains
- Oceanic-continental convergence: oceanic plate collides with continental plate, forming mountains
- Arc-continent collision: oceanic plate collides with continental plate, forming mountains
Examples include the Himalayan mountain range (Indian plate colliding with Eurasian plate) and Andes mountain range (Nazca plate subducting under South American plate)