Science Chapter 5 Questions
What scientist helped to discover the process of sea-floor spreading?
Harry Hess
So, in what layer would you find the mountains?
The crust.
Oceanic crust consists mainly of what rock?
Basalt.
Continental crust consists mainly of what rock?
Granite.
By using your hands to demonstrate, describe the type of movement that occurs at each type of plate boundary.
...
Explain to your mother the process of sea-floor spreading.
...
What is the difference between the lithosphere and the asthenosphere?
1. The lithosphere is the top layer of the mantle and the asthenosphere is the second layer or middle layer of the mantle. 2. In the lithosphere, the rocks are solid and hard. In the asthenosphere, the rocks are still solid, but softer like plastic.
Two plates collide with each other at...
A convergent boundary.
What is the lower mantle?
About the same, the rocks are still solid.
Along what feature of the ocean floor does sea-floor spreading begin?
Along a mid-ocean ridge.
What is a deep-ocean trench?
An underwater canyon into which the rocks from sea-floor spread return to the mantle.
Why is it difficult to determine Earth's inner structure?
Because to study it, you would have to be able to get deep into Earth's core. It is impossible to get that far into Earth because the deeper that you go, the pressure and heat get higher and higher.
The transfer of heat by the direct contact of particles of matter is called...
Conduction.
What happens in Earth's interior to produce Earth's magnetic field?
Convection currents in the outer core. You must remember this for the test: if there is a question about currents that occur in Earth itself, the answer should be convection currents.
The process that powers plate tectonics is...
Convection currents.
Subduction of the ocean floor takes place at...
Deep-ocean trenches.
What two main types of evidence do geologists use to learn about Earth's interior?
Direct evidence from rock samples and indirect evidence from seismic waves.
What are the three types of plate boundaries?
Divergent, convergent, and transform boundaries.
Why are the oldest parts of the ocean floor no older than 200 million years?
Due to the process of subduction.
What evidence supported the idea of continental drift?
Evidence from land features, such as mountains. Evidence from fossils, such as Glossopteris and Mesosaurus. Evidence from climate, such as the findings of fossils of tropical plants in Spitsbergen.
What three types of evidence provided support for the theory of sea-floor spreading?
Evidence from molten rock, evidence from magnetic stripes, and evidence from drilling samples.
T/F: Slow movements of mantle rock called radiation transfer heat in the mantle.
F-answer is convection.
T/F: Mid-ocean ridges are places where oceanic crust sinks back to the mantle.
F-answer is deep-ocean trenches.
T/F: When two continental plates diverge, a transform boundary forms.
F-answer is that a diverging boundary forms.
How do rocks along the central valley of the mid-ocean ridge provide evidence of sea-floor spreading?
First, they look like pillows, which suggests that they formed from molten rock. Second, they were deposited in such a way that their magnetism lined up with the polarity of the Earth at the time that they were deposited. Finally, samples drilled from the rocks tell us their age, and the rocks further away from the ridge are older than those closest to the ridge.
How did fossils provide evidence for continental drift?
Fossils were found on two separate continents, and it would have been impossible for the animals to have swum that far.
How are seismic waves used to provide evidence about Earth's interior?
Geologists record seismic waves and study their speed and the paths they take to reveal information about deep in Earth. For example, using data from seismic waves, geologists have learned that Earth's interior is made of several layers.
How are oceanic and continental crust alike? They have solid rock.
How are oceanic crust and continental crust different? Oceanic crust is less dense than continental crust.
What is a convection current?
In a pot of water heating on a stove, the heated molecules begin to move faster and spread apart. This decreases their density so that the heated water rises to the top. The cooler water, because the molecules move slower and are bunched together, has a greater density, and it sinks to the bottom. This creates a current of heated water rising to the top, where it cools, and the cooler water then sinks to the bottom.
What is the asthenosphere of the mantle?
It is below the lithosphere, and here, the rocks are still solid, but soft.
Is the rock in Earth's mantle solid or liquid?
It is solid. It is very hot, but it is still solid.
Explain to Mom the theory of plate tectonics...
It is the theory that pieces of the Earth's lithosphere are in slow, constant motion, driven by convection currents in the mantle. As the plates move, they either collide, pull apart, or grind past each other.
Where would you expect to find the oldest rock on the ocean floor?
Just before a deep-ocean trench, because the oldest rocks are being swallowed by the trenches.
What are plates?
Kind of like pieces of the Earth's crust. If Earth was an egg, it would be the pieces of the broken egg.
Classify each of the following layers as liquid, solid, or solid but able to move slowly or bent:
Lithosphere-solid Asthenosphere-solid but able to move slowly or bent Lower mantle-solid Outer core-liquid Inner core-solid
What causes convection currents in the mantle?
Mantle rocks rise slowly from the bottom of the mangle toward the top because it is hot, and once at the top, it becomes cooler. The cooler rocks then sink back down in the mantle and the cycle repeats itself.
What are the three types of heat transfer?
Radiation, conduction, and convection.
How is heat transferred through space?
Radiation.
T/F: Continental crust is made of rocks such as granite.
T
T/F: The single landmass that broke apart 250 million years ago was Pangaea.
T
The relatively soft layer of the upper mantle is called...
The asthenosphere.
According to the hypothesis of continental drift, how would a world map have changed over the last 250 million years?
The continents were originally together in a Pangaea. As continental drift took place, the continents moved further apart, as they are today.
What will happen to the convection currents in the mantle if the Earth's interior eventually cools down?
The convection currents will stop. Remember that without the addition of heat, a convection current will stop.
Name two layers in the Earth in which convection currents take place.
The core and the mantle.
What is the final layer of Earth?
The core. But remember that the core also has two layers: The outer core and the inner core.
What is the crust composed of?
The crust is the outermost layer. It is a layer of solid rock that includes both dry land and the ocean floor.
List Earth's three main layers:
The crust, the mantle, and the core.
In what layer would you find the oceans?
The crust.
What is the lithosphere of the mantle?
The lithosphere is the top layer of the mantle PLUS the crust together. So, it includes mantle and crust.
Earth's mantle is made of three layers itself. What are they?
The lithosphere, the asthenosphere, and the lower mantle.
Under the crust is what next layer of Earth?
The mantle.
What is found in the core?
The metals iron and nickel.
In general, what happens to the density of a fluid as it becomes hotter?
The molecules move faster and spread out, and this decreases the density.
What is likely to occur at a plate boundary where oceanic crust collides with continental crust?
The oceanic crust slides beneath the continental crust.
How does the outer core differ from the inner core?
The outer core is a layer of molten, liquid metal. The inner core is a solid ball of metal.
So, look at this picture of the crust. Where is the crust the thickest?
Under the mountains.
Why did most scientists reject Wegener's hypothesis of continental drift?
Wegener could not explain just HOW continental drift occurred.
Who proposed the concept of continental drift?
Wegener.
