Discussion Questions Answer Key
Lesson 1 "The Earth's Layers"
- How did Andrija Mohorovicic discover that the Earth's crust is made of less dense rock than the mantle.
By studying earthquake waves. The waves moved at diferent speed and at different angles through the different layers .
- Write in your own words the definition of a discontinuity.
A discontinuity is the boundary between the layers of the Earth.
- Name the four layers of the Earth in order from the outside to the
center of the Earth.
1.Crust 2. Mantle 3. Outer Core 4. Inner Core
- What causes the mantle to "flow"?
The mantle flows because of convection currents that are caused by very hot material in the mantle rising, cooling, and then sinking. This circular pattern causes the mantle to flow.
- What are the two main metals that make up the outer and inner core?
Nickel and Iron
- Describe in your own words how the Earth's layers were formed. Card 2 "The Four Layers" will help you.
As the Earth cooled the densest, heaviest materials sank to the middle of the Earth. The lightest materials rose to the top. This material was made mostly of rock. Rock makes up the crust of the Earth. Denser rock makes up the mantle. The most dense materials, iron and nickel, make up the inner and outer core.
Lesson 2 "Pangea to the Present"
- In your own words explain what the Continental Drift Theory states.
The Earth's plates are moved very slowly, 1-4 inches per year, by convection currents emenating from the mantle. These plates have been moving for millions of years and continue to move today.
- How did Alfred Wegener try to prove that the continents of Africa and South America were once connected.
Alfred Wegener discovered that the magnetic bands in rocks from South America did not point ot the north pole as they should. If these rocks were moved to the position that Wegener though they were created then they did point ot the northpole. He also matched rocks from Africa and South America for mineral content and age.
- How did the ancient people of Japan explain earthquakes?
The Japanese explained that earthquakes were produced by a giant catfish called Namazu. This catfish lived under the Earth's surface and shook very violently when it was not kept under control by the god Kashima.
- How did the ancient Romans explain the presence volcanoes.
Vulcan, the god of weapons, used the volcanoes off the coast of the Roman Empire as his forge.
Lesson 3 "How Plates Move"
- What causes mountain building?
Mountains are formed from the Earth's plates movements. As plates crash into each other they push the crust up high into mountains.
- What is the difference between how folded mountains and block-fault mountains are formed.
Folded mountains form into rollercoaster like formations. The layers are bent but not broken. When block-fault mountains are formed the layers are pushed up and broken into high sharp peaks and valleys.
- How do dome mountains form?
Dome mountains form when the layers of the Earth don't break or fold but are pushed up into a rounded dome shape.
- In your own words explain what happens at a subduction zone.
Two plates come together, one overriding the other at a subduction zone. The oceanic plate, which is thinner and denser, is driven under the continetal plate and into the mantle. A deep ocean trench is produced at the subduction zone.
- In your own words explain what happens at a mid-ocean ridge.
Two plates are separating with magma welling up and filling the void with newly produced crust. These spreading plates are making the oceans wider and wider while the subduction zones are making the oceans smaller and destroying old crust.
- At a subduction zone what causes magma to rise?
The oceanic crust and the upper layer of the mantle melts as it is driven into the mantle. The oceanic crust is not as dense as the mantle is. Because this material is less dense it will rise.