Plate Tectonics Flashcards
What is a mid-ocean ridge?
Undersea volcanic mountain ranges.
Describe seafloor spreading
Molten rock from inside the Earth rises into the gap and cools and solidifies into new rock.
How is molten rock linked to Earth’smagnetic field?
Magnetic particles in molten rock align with Earth’s magnetic field and a magnetic record is stored within the ricks when they cool and solidify.
In relation to magnetism, what occurs on either side of mid-ocean ridges?
Reversed polarity
Describe the process of convection currents
Hot metallic core causes the mantle directly above it to heat up. The liquid rock created rises and is pushed aside by more mantle rising below it. As the hot liquid cools it spreads out and sticks to the bottom of the mantle layer. The process repeats.
How are convection currents placed in the mantle?
In convection cells.
Why do tectonic plates move?
Because of convection currents.
How does earthquake and volcanic activity relate to plate boundaries?
Most volcanic and earthquake activity occurs on the boundaries of plates.
What are the 3 types of plate boundaries and what do they mean?
Divergent - Plates pull apart
Convergent - Plates collide
Transform - Plates grind past each other.
Describe divergent boundaries and give some examples. Do they have more volcanic or seismic activity?
Plates form a gap where magma is pushed up from the mantle below. Mid-ocean ridges, African rift valley. More volcanic activity, little seismic activity.
Describe convergent boundaries.
A lighter plate floats on top while another plate dives below (subduction). North western edges of Pacific Plate, west coast of South America. Produces a combination of volcanic and seismic activity.
Describe continent to continent convergent boundaries.
Continents buckle and crumble against one another, gradually rising skywards. The Himalayas. Few volcanoes, but lots of earthquakes.
Describe transform boundaries.
Plates moving past one another store energy between them until the friction holding them gives way to form an earthquake. San Andreas fault, most others on ocean floor. Lots of earthquakes, only occasional volcanic activity.
