lecture 3 Flashcards
What is the significance of mid-ocean ridges in plate tectonics
Mid-ocean ridges are where new oceanic crust is created, mostly from basalt, aligned with Earth’s magnetic field at the time of cooling. This crust is denser and can subduct beneath less dense crust.
What is the difference between True North and Magnetic North?
True North is a fixed point where all lines of longitude intersect, depicted as ‘up’ on maps. Magnetic North, which changes over time, aligns with Earth’s magnetic field and is what a compass needle points to.
What stages are involved in the Wilson Cycle?
The Wilson Cycle models the life cycle of ocean basins through stages: Embryonic, Juvenile, Mature, Declining, Terminal, and Suturing. One cycle spans many millions of years.
What are Ridge Push and Slab Pull?
Ridge Push occurs as new crust at a mid-ocean ridge pushes old crust down the slope due to elevation differences. Slab Pull is when subducting crust sinks into the mantle due to its higher density.
How can seafloor features be measured?
Features can be measured using echo sounders that send a sound signal to the ocean floor and record the echo, modern techniques like multibeam echo sounders, or through satellite-derived bathymetric maps.
What are Hotspots?
Hotspots are volcanoes within a tectonic plate, formed by intense volcanic activity at a rising mantle plume. They can track the movement of tectonic plates over time.
What are Seamounts and Tablemounts?
Volcanoes formed on the ocean floor, either over a hotspot or at a mid-ocean ridge. Seamounts are cone-shaped, while tablemounts are flat-topped underwater volcanoes.
What are the main features of a continental margin?
Features include the continental shelf, slope, and rise. The shelf is flat and shallow, the slope is steeper, and the rise is the transition zone to the deep ocean floor.
What characterizes deep ocean basins?
Deep ocean basins include the abyssal plain (flat surfaces), abyssal hills, seamounts, tablemounts, ocean trenches, volcanic arcs, and mid-ocean ridges.
What are Hydrothermal Vents?
Fissures on the seafloor that emit heated water, associated with volcanic activity. They host unique ecosystems reliant on chemosynthesis, with extreme conditions like high temperatures and toxic minerals.
