Plate Tectonics 1
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Plate Tectonics 2
Earthquakes
Volcanoes
100
What causes the convection current in the mantle?
Heat from the core
100
Define bomb. Explain where bombs come from. (in the context of volcanoes)
A bomb is a piece of rock expelled from a volcano that is bigger than a softball. Bombs are caused during massive explosive volcanic eruptions where the whole top of the mountain explodes and creates a pyroclastic flow.
100
What type of plate boundary are mid-ocean ridges and rift valleys? What is the difference between a mid-ocean ridge and a rift valley?
Divergent plate boundaries result in mid-ocean ridges and rift valleys. A mid-ocean ridge is in the middle of the ocean and a rift valley is on a continent.
100
How does the energy released from an earthquake travel through the earth?
Seismic waves
100
What is the difference between magma and lava?
Magma is the name for the mixture of molten rock, water, and gases when it is beneath the earth's surface, while lava is the name for the mixture once it is above the earth's surface.
200
Why does the crust float on top of the mantle?
The crust is less dense than the mantle.
200
What is the primary reason volcanoes erupt?
Expanding gas pushes magma to the surface.
200
What type of feature exists at a convergent plate boundary where oceanic crust is subducted under continental crust?
Deep ocean trenches exist at subductive convergent plate boundaries.
200
What do P and S stand for in the context of P-wave and S-wave? Why do these waves have these names?
P stands for Primary (meaning first) and S stands for Secondary. They are named based on how quickly they arrive after an earthquake.
200
What are the three ingredients in magma? Where do these ingredients come from?
The three ingredients include molten rock, water, and gases. These ingredients are supplied by the subduction of water and oceanic crust at subductive convergent plate boundaries.
300
Why did scientists reject Alfred Wegner's theory of continental drift at first?
Wegner's theory was initially rejected because he could not explain why continental drift was happening.
300
What is the term for the device that shows seismic activity by drawing lines on a paper?
A seismograph shows seismic activity by drawing lines on a paper, bigger lines mean bigger earthquakes, smaller lines mean smaller earthquakes.
300
What are three main pieces of evidence that Wegner used to support his theory of continental drift?
1. Fossils from the Mesosaurous on South America and Africa. 2. Coal deposits in the arctic (coal only forms under rain forests) 3. Glacier marks in the South African desert.
300
What is triangulation? How do scientists use triangulation to locate the epicenter of earthquakes?
Triangulation is where scientist use data from three different seismographs to draw three circles that all intersect at one point and that is the epicenter. Each circle is draw using the time between the arrival of the p wave and arrival of the s wave to determine the radius.
300
What type of plate boundaries forms most volcanoes? How are volcanoes that are not on a plate boundary formed?
Convergent boundaries where there is subduction happening cause most volcanoes. Volcanoes that are not on a plate boundary are formed by a hot spot, like the volcanoes on the Hawaiian islands.
400
What are the three types of plate boundaries? Describe the plate movement at each boundary by drawing arrows.
Convergent ---><---- Divergent <--- ----> Transform <====>
400
What viscosity of magma (high viscosity or low viscosity) would cause a volcanic eruption that would lead to a pyroclastic flow?
High viscosity magma would be more resistant to flow, meaning it would take a lot more pressure build up to get it to move. If that much pressure built up, it would lead to an explosive eruption and a pyroclastic flow if the whole top of the volcano exploded.
400
How do scientists know how often the Earth's magnetic poles reverse?
Scientists look at bands of rock on the sea floor. Depending on which way the poles were arranged, the rocks look different.
400
How is the moment magnitude scale different from the Richter scale in terms of how scientists measure the size of earthquakes?
Moment magnitude scale is more accurate than the richter scale because it tells how much energy was released during an earthquake. In the Moment Magnitude Scale, scientist measure the surface area of the fault and how much the fault moves to determine how much energy was released, compared to the Richter scale where scientists look at seismographs and see how big the wavy lines get.
400
What are the three phases of volcanic activity? Which of these describes a volcano that appears to be asleep but may reawaken to erupt again in the future?
Volcanoes can be extinct, dormant, or active. Dormant volcanoes appear to be asleep but may erupt in the future.
500
Why does oceanic crust subduct under continental crust?
Oceanic crust is more dense than continental crust so it will sink during subduction.
500
Which is more powerful and releases more energy, an atomic bomb or a volcano?
A explosive volcanic eruption is thousands of times more powerful than an atomic bomb.
500
According to Grandpa, what causes movement of all the plates and therefore earthquakes and volcanoes?
Convection currents in the mantle ultimately cause movement of all the plates and thereby cause all earthquakes and volcanoes.
500
What are the three main types of seismic waves? Which travels fastest? Which causes the most damage/move the ground the most?
The three waves are p-waves, s-waves, and surface waves. P-waves travel the fastest through the ground like smooshing a slinky. Surface waves cause the most damage because they actually move the surface of the earth where all the buildings are built.
500
What is the most dangerous volcanic hazard? What is the best way to protect yourself from this hazard?
The most dangerous volcanic hazard is a lahar! The best way to protect yourself from a lahar is to get to high ground or evacuate the flood zone!
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