Chapter 04 The Way the Earth Works: Plate Tectonics guided learning

As plates move, they collide, pull apart, and slide past one another. Drag each plate boundary name to the corresponding image.

- convergent - transform - divergent

Plate motion leads to the building of mountains and the occurrence of large earthquakes every year. How far will an average plate move over the course of a year?

a few centimeters

Volcanic rocks are usually very easy to numerically date. You can see the ages of each of the eruptions along the Yellowstone hot spot (in millions of years) written in white. We can also estimate the distance between the volcanic calderas using the scale in the upper right-hand corner. We can use the equation velocity = distance/time to calculate how fast the North American Plate is moving. Using the scale and the ages of McDermitt volcanic field (16 million years) and Yellowstone (0.6 million years), calculate the velocity of the Pacific Plate's motion in cm/year (Hint: there are 100,000 cm in a km).

approximately 5cm/year

Now select the area where the oldest oceanic crust is located.

blue part (oldest oceanic crust is at the continental margin)

Which processes are responsible for driving plate tectonics?

correct: - ridge push - slab pull - convective shear incorrect: - Milankovitch cycles - centrifugal force

It is clear that the North American Plate is moving over the Yellowstone hot spot. What may be less clear is the rate at which this movement is taking place. To answer that question, we need to calculate the velocity of the North American Plate. How do you calculate velocity? Place the three provided terms correctly into the equation.

distance/time = velocity

On the following map, there are six boxes at different tectonic margins. Drag the label of active or passive to the appropriate areas.

from left to right: 1) active 2) active 3) passive 4) passive 5) active 6) passive

On the following map, there are six boxes at different plate boundaries. Using the arrows showing relative plate motion, label each box as a convergent or divergent plate boundary.

from left to right: 1) convergent 2) divergent 3) divergent 4) divergent 5) convergent 6) convergent

Let's look at subduction zones in more detail. Label the different parts of the subduction zone using the terms below.

from left to right: 1) lithospheric mantle 2) continental volcanic arc 3) accretionary prism 4) asthenosphere

On the following map, there are four boxes at different tectonic settings. Drag the labels of the tectonic settings to the appropriate areas.

from left to right: 1) passive margin 2) mid ocean ridge 3) volcanic island arc 4) subduction zone

On the following map, there are six boxes at different plate boundaries. Identify which plate boundaries display seismicity and volcanism and those that produce seismicity without volcanism.

from left to right: 1) seismicity alone 2) seismicity and volcanism 3) seismicity and volcanism 4) seismicity and volcanism 5) seismicity alone 6) seismicity alone *Neither transform plate boundaries nor continent-continent collisions are associated with volcanism because there is no subduction.

The following diagram shows the different parts of the Earth's crust and mantle. Label the continental crust, oceanic crust, lithospheric mantle, and asthenosphere.

from top to bottom: - continental crust/oceanic crust - lithospheric mantle - asthenosphere

The theory of plate tectonics proposes that the Earth's rocky exterior is broken up into several pieces, or plates, that move with respect to one another. What is the rigid outer layer of the Earth called?

lithosphere

If the Emperor seamounts were formed by hot spot eruptions 70 million years ago and Hawaii was formed by modern eruptions, which way has the Pacific Plate moved? Remember that hot spots remain stationary while the plate moves over them, creating the island chains.

north, then northwest

Based on the description of hot spots provided in the video, select the oldest volcano in the chain of islands pictured below.

one on the left

Examine this image of an ocean basin, and select the continental crust.

one with land

This image shows an oceanic basin. The mid-ocean ridge is on the right and the continental margin is on the left. Which term best describes the continental margin shown here?

passive margin (occurs where continental crust transitions to oceanic crust without crossing a plate boundary)

Based on the direction of plate motion you just determined, where would you expect the next large eruption to occur?

southern Montana

Volcanic hot spots can help us understand the direction that tectonic plates have moved through time. For example, if you look at the map below, you can see how the Yellowstone hot spot (red circles) started out beneath southern Oregon (McDermitt volcanic field). Today, the hot spot is located in northwest Wyoming (Yellowstone). Hot spots do not move. What you are seeing is the result of the North American Plate moving over the last 16 million years. In what direction has the North American Plate moved?

southwest

Examine the set of plate boundary images, and select the one that shows subduction.

the one where arrows move towards each other

Ultimately, plate motion is something that rarely affects our everyday lives. However, the process is continuous and relentless, building mountains and occasionally reminding us of its presence by causing earthquakes. So, what does it mean for the future? We know that along the San Andreas fault, the Pacific Plate (upon which Los Angeles sits) is moving north at a rate of 5 cm/year compared to the North American Plate (upon which San Francisco sits). At this rate, how long will it be until Los Angeles is a suburb of San Francisco? San Francisco is 550 km north of Los Angeles.

~11 million years