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Layers of Earth, Types of Crust, Continental Drift and Seafloor Spreading
Date ___________
Layers of Earth (from the inside out)
_____________ ______
______________________: solid; 2 types (oceanic and continental)
____________________________________ (broken into “plates”)
______________________: solid
____________________
______________________: hot, taffy-like layer; this is what the “plates” move on
when driven by convection currents
______________________: solid
______________________: liquid Fe and Ni
___________________
______________________: solid Fe and Ni
(hottest part; under great pressure)
Two Types of Crust
Continental Crust
Oceanic Crust
Rock Type
Color
Composition
Density
Avg. Thickness
Depth
(general)
Continental Drift
Hypothesis proposed by _________________________________, a German Scientist, in 1912
A theory that at one time all the continents were joined as one supercontinent called ________________ (Greek word
meaning “all the earth”), and over time have been drifting apart. Continental Drift gave an explanation to finding similar
organisms, rock types and past glacial activity on several different continents – in Wegener’s time and today.
Wegener thought the continents were pushing through a stationary ocean floor but ________________________, so
many people rejected his theory.
Technological Advances
In the early 1900s most people, including scientists, believed that the ocean floor was flat. Advances in technology in the
1940s and 1950s proved this theory to be wrong.
______________________, a type of echo sounding device that uses sound waves to measure water depth, is one
advance that allowed scientists to study the ocean floor in detail.
Another advance was the ___________________________, a device that can detect small changes in magnetic fields.
This is a great tool because the ocean crust has a lot of ____________ in it.
Maps were made using sonar and magnetometer data and showed scientists that the ocean floor had different
landforms like they saw on Earth’s surface.
Topographic maps were made from sonar and magnetometer data that helped to discover vast, underwater mountain
chains called _____________________________, and underwater ditches called ________________________________.
The longest mountain chain in the world is the ____________________________, found in the ______________ Ocean.
The deepest trench is the ________________________, found in the ________________ Ocean.
Scientists found that rock samples taken from areas near ocean ridges were ________________ than samples taken
from areas near deep-sea trenches. This was indicated on their maps using lines called ____________________, or lines
on a map that connect areas of sediments that have the same age.
Using sonar, topographic and age information from the new technology, American Scientist _____________________
proposed Seafloor Spreading in the mid-1900s. His theory states that
_______________________________________ and ______________________________________________.
**Note: Seafloor Spreading was the missing link needed by Wegener to complete his model of continental drift.