Planet Earth: Topic 4 - The Moving Crust
1. Compared to the other layers of the Earth, the crust, at a temperature of 5oC is ...
x thicker than the upper mantle
thinner than all the layers
(Text p. 382) Figure 5.35 The Crust is only 5 - 60 km thick.
x thicker than the lower mantle
x thicker than any other layer
Alfred Wegner determined that the continents at one time all fit together to form one large
supercontinent, called Pangaea. Their interlocking shapes and other evidence helped him form the
Theory of Continental Drift. The other evidence was ...
x discovery of land bridges connecting the continents
x similar trees on different continents
fossil evidence indicating the continents has been joined
(Text pgs. 383-384) Wegener studied the fossil evidence
x lower ocean level with islands close together
Glaciers once existed in the southern hemisphere. The evidence Wegener found to prove this were
x morraines found
x erratics found
(Text p. 385) Under the ancient glacial deposits, there were grooves (abrasions) in the
bedrock, showing the direction in which the glaciers moved.
x ice caves
Advances in technology helped to prove Wegener's theory long after his death. The patterns of
magnetic reversals on the ocean floor lead scientients to the theory of sea-floor spreading. The
instrument scientists used to detect the direction and strength of the magnetic field is called ...
(Text p. 388) Magnetometers are electronic instruments tht can detect the direction asnd
strength of a magnetic field.
When scientists discovered the ridges along the ocean floor, they also found lava coming out of the
cracks in the sea floor. This type of lava is called ...