Plate Tectonics Flashcards
Why do humans struggle to comprehend Earth’s movement?
Due to the long geological timescales involved.
What hindered the understanding of geological phenomena before plate tectonics?
The static Earth viewpoint, which lacked a dynamic model of Earth.
What evidence supported the theory of continental drift?
Fit of continents.
Exploration of the ocean floor in the 1950s.
By the late 1960s, plate tectonics incorporating continental drift gained acceptance.
What challenges are involved in seafloor exploration?
Depth of water and high pressures in the deepest parts.
Traditional methods using ships lacked automation and data storage.
What was the significance of the Mid-Atlantic Ridge discovery?
Confirmed by Marie Tharp and Bruce Heezen, it revealed a massive ridge and systematic topography of the ocean floor.
What systematic features were discovered on the ocean floor?
Depth increases away from ridges toward ocean trenches.
Sediment thickness and rock composition vary systematically.
Fresh volcanic rocks near ridges, with increasing sediment thickness away from them.
How do magnetic field variations support seafloor spreading?
Symmetrical magnetic fluctuations on both sides of ocean ridges.
Consistent bands of magnetic intensity aligned with ridge axes.
Correlation with magnetic reversals in continental rocks.
What did ocean drilling confirm about seafloor spreading?
Sediment thickness and age increase with distance from the ridge axis.
Supported paleomagnetic inferences of active crust formation at ridges.
What are the rates of seafloor spreading?
Ranges from 1 to 20 cm per year, comparable to the growth rates of human hair and fingernails.
How are earthquakes distributed globally?
Occur in well-defined belts along ocean ridges and Benioff zones.
Shallow earthquakes along ridges, deep earthquakes in subduction zones.
What role do transform faults play in plate tectonics?
Host earthquakes due to opposite crustal movement along ridges.
Some extend through continents, causing high seismicity zones like the San Andreas Fault.
What is the theory of plate tectonics?
Earth’s surface consists of mobile plates gliding over the asthenosphere.
Plates form at divergent boundaries, subduct at convergent boundaries, and slide past each other at transform faults.
How does ocean depth change with plate evolution?
Plates thicken and sink into the asthenosphere with age.
Ocean depth changes linearly with the square root of age.
What are the key consequences of plate tectonics?
Mountain formation at convergent margins.
Oceanic crust renewal at spreading centers.
Earthquake and volcanic activity from plate movements.
Continental fit and seafloor spreading explained.
Sediment scarcity due to plate recycling.
Biological differences correlate with continental drift.
How do GPS measurements verify plate tectonics?
Direct measurement of plate velocities confirms predicted movements.
Align with rates inferred from paleomagnetism.
