Continental Drift and Plate Tectonics

Continental Drift Theory

• Wegener's theory of continental drift proposed that continents were once joined as a single landmass (Pangea) and have drifted apart.
• Wegener's observations included similar fossils found on different continents and the matching shapes of continents, suggesting they were once connected.
• The theory was initially met with skepticism because Wegener couldn't explain how the continents moved.
• Evidence supporting continental drift included similar fossils and rock formations on different continents (e.g., Cynognathus reptile fossils found in both South America and Africa).

Plate Tectonics

• The Earth's crust is composed of large, moving plates.
• Convection currents in the Earth's mantle cause the plates to move.
• The theory of plate tectonics explains the movement of the continents and the formation of mountain ranges, volcanoes, and earthquakes.
• Plate movements explain the formation of the mid-Atlantic ridge as evidence of continental drift.
• New evidence in the 1950s and 1960s supported the theory of continental drift.

Marie Tharp

• Marie Tharp was a geologist and cartographer who mapped the ocean floor.
• Her maps identified the mid-Atlantic rift, a deep valley in the ocean floor.
• Tharp's work provided important evidence supporting the theory of continental drift.
• Her work was crucial in understanding the movement and interactions of the plates.