Continental Drift Flashcards
What was Alfred Wegener’s idea of continental drift?
The Earth’s continents were once joined together, but gradually moved apart over millions of years
What is ‘seafloor spreading’?
In the centres of many oceans, there are mid-ocean ridges. At these places, the tectonic plates are moving apart. Molten material, known as magma from inside the Earth oozes out and solidifies
What is the typical speed of ‘seafloor spreading’?
Around 10cm a year
How are volcanoes produced?
If the plates are moving apart, as at mid-ocean ridges, volcanoes are produced as molten magma is allowed to escape
How are mountains produced?
If the plates are moving towards each other, the edges crumple and one plate ‘dives’ under the other
How do earthquakes occur?
If the plates are moving sideways, stresses build up at the plate boundary. When the stress reaches some critical value, the plates slip suddenly, causing an earthquake
What is a tsunami?
An earthquake which occurs at sea
