10.1 Moving Continents

Question 1

What are the Layers of Earth?

Answer 1

Crust (lithosphere, rigid rock)
Upper mantle (lithosphere, rigid rock)
Lower mantle (Asthenosphere, semi liquid)
Outer core (Nickle + Iron. Liquid)
Inner core (Iron. Solid)

Question 2

What is Crust?

Answer 2

-Outermost layer of Earth
-Ranges from 5 to 30km in thickness
-Broken into large sections called tectonic plates which move around on top of the semi-liquid asthenosphere

Question 3

What are the Tectonic Plates?

Answer 3

Pacific Plate
Australian Plate
North American Plate
South American Plate
African Plate
Antarctic Plate
Indian Plate
Arabian Plate

Question 4

What are the Types of Crust?

Answer 4

-Continental: Thicker, less dense, contain lighter elements like aluminum and silicon
-Oceanic: Denser, thinner, contains heavier elements like iron and magnesium
-Mix

Question 5

Who is Alfred Wegener?

Answer 5

-German Scientist
-If you cut out and rearranged present-day continents, they actually fit together like a jigsaw puzzle
-Theory of continental drift: Pangaea, supercontinent, 200 million years ago all of the continents were once joined together
-Fossils of the same species were found on now widely separated continents
-The scientific community rejected Wegener’s ideas and he was forgotten for almost fifty years Because he couldn’t explain how the continents moved
-After World War II, many new discoveries were made which forced scientists to revisit Wegener’s ideas.
They observed the ocean floor with new sonar technology

Question 6

Who is Mary Tharp?

Answer 6

-female scientist who painstakingly organized that data and created the first map of the seafloor
-The seafloor was NOT flat, she discovered huge underwater mountain chains
-These underwater mountain ranges had active volcanoes and were 3000m tall and over 45,000 km long
-Chains (aka ridges) were called the GREAT GLOBAL RIFT SYSTEM
-Besides these huge mountain chains, they also found deep trenches (over 7km deeper than the average ocean floor)
-cracks between continents is another piece of evidence for Wegener’s theory of continental drift

Question 7

Who is Harry Hess?

Answer 7

-a naval scientist
-proposed the theory of seafloor spreading: Magma from the active volcanoes at the underwater mountain ridges was forming “new” crust and pushing the seafloor outwards,
“Old” seafloor was somehow disappearing into the deep underwater trenches
-Age of Seafloor: Rock near the ridges were relatively YOUNG, While rock near the trenches were relatively OLD
-The layer of sediment near ridges were thinner (young rock = less time for sediment to accumulate)
The layer of sediment near trenches were thicker (older rock = more time)
-Magnetic Striping: Earth’s magnetic field is always changing – the magnetic North and South flip every 300,000 years or so. New ocean crust forms at mid-ocean ridges, carrying Earth’s magnetic record as it spreads, creating symmetrical patterns.

Question 8

Why does Plates Move?

Answer 8

1. Convection Currents:
   Hot magma rises from the asthenosphere, hitting the plates and pushing them before cooling and sinking to the asthenosphere.
   2.Gravity:
   Slab pull: gravity pulls on the heavier oceanic crust near the trenches – pulling the rest of the plate into the mantle.
   Ridge push: magma new crust forms at the ridge and pushes the older crust away.