Flashcards in Earth and space sciences Deck (10)
State the layers of the earth.
-Crust, mantle, core.
-lithosphere (crust + upper mantle)
-asthenosphere (middle mantle)
What is the continental drift theory?
All continents were once connected to each other. This landmass was referred to as Pangea.
Explain three pieces of supporting evidence behind the continental drift theory.
- The continents seemed to fit together like a jigsaw.
- fossils of the same prehistoric species were found on continents that were long ways apart; there was no way that the organisms (like plants) could cross the oceans and reach all these places.
- rock formations / sediments
Describe the process of sea floor spreading.
As the plates diverged, new rocky crust was being formed at the ocean ridges and spreading outwards.
Describe the process of subduction.
The process of the denser plate sinking down below another plate where is melts and is destroyed.
State three pieces of supporting evidence behind sea floor spreading.
- magnetic striping
- age of the sea floor
- sediment thickness
Explain magnetic striping.
- magnetic striping: many rocks contain magnetite which is magnetic and contains south and north seeking poles. When the molten rock solidifies, the magnetite lines up with the earths magnetic field which is preserved in that rock. manometers can detect the magnetic field of these rocks and showed that these were bands of weak and strong alternating bands parallel to the mid ocean ranges and the farther away they went from the ridge, the magnetic field in the rock kept changing, indicating that the earth's magnetic field flips every few million years.
explain Age of the sea floor
- the further the rocks of the sea floor were from the ridges, the older they were
- the oldest seafloor rocks are only about 200 million which is very young compared to continents.
explain sediment thickness
sedimentary rock layers become thicker as you move away from the ridges because the sediments had been falling for longer on the older rocks.