3 plate tectonics Flashcards
how many plates are there?
12 major
where are oceanic trenches?
at plate boundaries between land and sea
where are mountain ranges?
on land at plate boundaries
where are oceanic ridges?
in the middle of the ocean
what idea did wegener propose?
continental drift
whats the continental drift?
idea that earth’s continents drifted from each other over time
what evidence is there for continental drift?
biology, botany, geology
what idea did hess propose?
seafloor spreading
what is seafloor spreading?
as two plates separate, magma rises up to fill the opening
how can the theory of seafloor spreading be tested?
using magnets
what do basalt rocks include?
iron, naturally magnetic
how are ocean floors surveryed today?
ships towing a magnetometer
what was in the seafloor?
stripes of alternating magnetic polarity, and mirror images on either side of mid-ocean ridges
