TECTONIC PLATES
What is a tectonic plate?
A large, rigid piece of Earth's lithosphere that moves relative to other plates.
Who proposed the idea of continental drift?
Alfred Wegener.
What type of evidence was found on continents that are now separated by oceans?
Matching fossils.
Where does new oceanic crust form?
At mid-ocean ridges.
What does paleo mean in paleomagnetism?
Ancient.
What part of Earth is divided into tectonic plates?
The lithosphere.
What is continental drift?
The idea that continents have moved over Earth's history.
What evidence involves similar rock formations on continents that are now separated?
Matching rock layers and geological structures.
What is seafloor spreading?
The process in which new oceanic crust forms at mid-ocean ridges and moves away from the ridge.
What is paleomagnetism?
The study of Earth's ancient magnetic field as recorded in rocks.
About how fast do tectonic plates usually move?
A few centimeters per year.
What was the name of Wegener's supercontinent?
Pangaea.
What does ancient climate evidence tell scientists?
It suggests that continents have changed positions over time.
What happens when magma reaches a mid-ocean ridge?
It cools and forms new oceanic crust.
How can rocks record Earth's magnetic field?
Magnetic minerals in molten rock can align with Earth's magnetic field as the rock cools and becomes solid.
Are tectonic plates the same thing as continents?
No. A plate can contain continental crust, oceanic crust, or both.
What did Wegener notice about the coastlines of South America and Africa?
They appeared to fit together like puzzle pieces.
Why are matching fossils on different continents evidence of continental drift?
Some organisms could not have crossed huge oceans, suggesting the continents were once connected or much closer together.
What pattern did scientists discover in the rocks on the ocean floor?
Alternating magnetic patterns that are symmetrical on both sides of the mid-ocean ridge.
Why are symmetrical magnetic stripes on the seafloor important evidence?
They show that new crust formed at the mid-ocean ridge and moved outward in both directions.
What happens to continents as tectonic plates move?
The continents move because they are part of the tectonic plates.
Why wasn't Wegener's idea immediately accepted?
He had evidence that continents had moved, but he could not provide a convincing mechanism explaining how they moved.
Name four types of evidence that supported continental drift.
Matching coastlines, matching fossils, matching rocks, and ancient climate evidence.
Explain how seafloor spreading provides evidence that tectonic plates move.
Magma rises at mid-ocean ridges, cools to form new crust, and the new crust moves away from the ridge, showing that the ocean floor is spreading.
Scientists found matching fossils, matching rocks, ancient climate evidence, seafloor spreading, and magnetic patterns. What major scientific theory do these pieces of evidence support?
The theory of plate tectonics.