Question

plate tectonics
what is continental drift?

1. who came up with the theory of continental drift?
2. explain the 4 main pieces of evidence that led to the theory of continental drift.

why do tectonic plates move?

1. how is the movement of tectonic plates measured?
2. how do convection currents drive the movement of tectonic plates?
3. what other factors are at play in making plates move?
4. when an oceanic plate meets a continental plate, the oceanic plate is subducted under the continental plate. what can you infer about the density of the two plates?

Explanation:

1. Alfred Wegener proposed the theory of continental drift.
2. - Jigsaw - fit of continents: The coastlines of continents like South America and Africa seem to fit together like pieces of a puzzle.

• Fossil evidence: Similar fossil species (e.g., Mesosaurus) are found on continents that are now separated by oceans.
• Rock formations and mountain ranges: Matching rock types and mountain belts (e.g., Appalachian and Caledonian mountains) on different continents.
• Paleoclimate evidence: Glacial deposits in regions that are now tropical, indicating past continental positions closer to the poles.

1. The movement of tectonic plates is measured using Global Positioning System (GPS) technology. GPS receivers placed on the Earth's surface can detect very small movements (on the order of millimeters per year) of the ground, which corresponds to the movement of the tectonic plates.
2. Convection currents in the mantle drive plate movement. Hot, less - dense material rises in the mantle, while cooler, denser material sinks. This circular motion (convection) exerts a force on the overlying tectonic plates, causing them to move.
3. Other factors include ridge push (gravity - driven force at mid - ocean ridges where new crust is formed and pushes the plates away) and slab pull (the dense, subducting oceanic plate pulls the rest of the plate along as it sinks into the mantle).
4. When an oceanic plate is subducted under a continental plate, we can infer that the oceanic plate is denser than the continental plate. Density differences are a key factor in subduction, with the denser plate (oceanic, due to its composition of basaltic rocks) sinking beneath the less - dense continental plate (composed of granitic rocks).

Answer:

1. Alfred Wegener.
2. - Jigsaw - fit of continents.

• Fossil evidence.
• Rock formations and mountain ranges.
• Paleoclimate evidence.

1. Using Global Positioning System (GPS) technology.
2. Convection currents in the mantle (hot material rises, cool material sinks, exerting force on plates).
3. Ridge push and slab pull.
4. The oceanic plate is denser than the continental plate.