EOM: Plate Tectonics

Emma and Zoe are studying ocean basin formation in their geology class. They look at a diagram showing the formation process. Which statement identifies the youngest bands of rock and how they were formed?

• A. A and L are the youngest. The newest rock forms at the edges and moves toward the center as it ages.

• B. F and G are the youngest. The newest rock forms at the center and moves toward the edges as it ages.

• C. A and F are the youngest. The newest rock forms on the left and moves toward the right as it ages.

• D. G and L are the youngest. The newest rock forms on the right and moves toward the left as it ages.

Answer explanation

The correct choice is B. F and G are the youngest because new rock forms at the center of the ocean basin and moves outward as it ages, indicating that the youngest rock is found at the center.

Noah and Maya are studying the distribution of fossils as evidence for plate tectonics. They examine the distribution of four different fossil organisms over three different continents. The distribution of which organisms can be used as evidence that Africa was once connected to South America?

• Lystrosaurus, Mesosaurus, and Glossopteris

• Cynognathus, Glossopteris, and Lystrosaurus

• Glossopteris, Cynognathus, and Mesosaurus

• Cynognathus, Mesosaurus, and Lystrosaurus

Answer explanation

Lystrosaurus, Mesosaurus, and Glossopteris are found on both Africa and South America, indicating these continents were once connected. Their fossil distribution supports the theory of continental drift.

The earthquakes experienced in California are related to tectonic plates. These events are the result of what process?

• Two tectonic plates sliding past each other

• Tectonic plates melting as they slide into the mantle

• Tectonic plates being weathered over time

• Two tectonic plates pulling away from each other

Answer explanation

The earthquakes in California occur due to two tectonic plates sliding past each other, a process known as lateral faulting. This movement causes stress to build up, leading to seismic activity.

Sophia and Michael are studying a diagram that shows evidence of geologic change in an area. The labels for each area are as follows: - A is sandstone. - B is shale. - C is limestone. - D is igneous basalt. Which sequence best describes the area’s geologic history?

• The rock layers were deposited in this order: limestone, shale, sandstone. Then, a fault moved the layers. Finally, magma pushed into the rock.

• The rock layers were deposited in this order: limestone, shale, sandstone. Then, magma pushed into the rock. Finally, a fault moved the layers.

• The rock layers were deposited in this order: sandstone, shale, limestone. Then, magma pushed into the rock. Finally, a fault moved the layers.

• The rock layers were deposited in this order: sandstone, shale, limestone. Then, a fault moved the layers. Finally, magma pushed into the rock.

Answer explanation

The correct sequence is sandstone, shale, limestone, indicating deposition order. Afterward, magma intruded, followed by a fault movement, which aligns with geological processes.

Isla and her friends were studying about the Hawaiian Islands in their geography class. Their teacher explained that these islands are an example of hot spots, a type of landform caused by plate tectonics. Which of the following correctly identifies how hot spots are formed?

• Hot spots are formed on land when magma escapes from the crust, and the plate moves over time, causing a chain of new land formations.

• Hot spots are formed when a volcano erupts on land.

• Hot spots are formed when a volcano erupts in the ocean.

• Hot spots are formed in the ocean when magma escapes from the crust, and the plate moves over time, causing a chain of new land formations.

Answer explanation

Hot spots form in the ocean when magma escapes from the crust. As tectonic plates move over these stationary magma sources, they create a series of volcanic islands, like the Hawaiian Islands.

Mason and Anika are studying plate tectonics and are looking at a map showing plate boundaries around the world. At which of the following boundaries would they expect volcanoes to form? Click the boundaries where volcanoes form.

• Boundary 1

• Boundary 2

• Boundary 3

• Boundary 4

• Boundary 6

Answer explanation

Volcanoes typically form at divergent and convergent boundaries. Boundary 1 and 2 are likely divergent, while Boundary 4 and 6 are convergent, making them suitable for volcanic activity.

Ava, Hannah, and Arjun are studying tectonic plate boundaries for their geography project. They have listed characteristics of three types of boundaries. Identify the plate boundary described in each column.

• Convergent Boundary

• Divergent Boundary

• Transform Boundary

Answer explanation

A convergent boundary occurs where plates collide, a divergent boundary forms where they move apart, and a transform boundary is where they slide past each other. Each type has distinct geological features.

Isla and Kai are studying supervolcanoes, which are huge, violent eruptions that produce greater than 1,000 cubic kilometers of Earth material. These eruptions are rare, with only an estimated dozen of them erupting about every 100,000 years. Which of the following descriptions could involve supervolcanoes?

• A large magma plume pushes up into Earth’s crust. The plume pools because it cannot break the crust.

• Plates pull apart on the ocean floor. Magma rises up through the cracks in the crust, spills out, and cools.

• Enormous pressure builds in the magma plume until it explodes through the crust.

• The continued, gentle explosion of magma through the central vent flows down the sides and creates a cone shape.

• The sharp contraction of magma after the explosion causes the rock above to collapse into a large crater, or caldera.

Answer explanation

Supervolcanoes involve large magma plumes that build pressure until they explode through the crust, creating calderas. The other options describe different volcanic processes not specific to supervolcanoes.

Liam and Avery are studying the history of Earth’s magnetic poles. They learn that over time, these poles have reversed. Rocks containing iron provide a record of these changes through bands that are formed. They refer to a diagram of the Mid-Atlantic Ridge. The pattern of normal and reversed magnetic bands on either side of the Mid-Atlantic Ridge provides evidence of plate tectonic activity at–

• transform boundaries.

• convergent boundaries.

• divergent boundaries.

• strike-slip boundaries.

Answer explanation

The pattern of normal and reversed magnetic bands on either side of the Mid-Atlantic Ridge indicates that new oceanic crust is formed as tectonic plates diverge, providing evidence of divergent boundaries.

During a geology class, Daniel and Abigail learned that over the course of Earth’s history, the magnetic poles of Earth have reversed. Rocks that contain iron provide a record of normal and reversed magnetic poles because of the bands that are formed. Refer to the diagram of the Mid-Atlantic Ridge. Which statement best explains the answer to Part A?

• The symmetric pattern shows where plates are moving away from each other.

• The bands of rock showing normal and reversed poles are not all the same width.

• The composition of the rock changed every time the plates pushed against each other.

• The deposits of iron in the rock were only made when the plates stopped moving.

Answer explanation

The symmetric pattern of magnetic bands at the Mid-Atlantic Ridge indicates that new rock is formed as tectonic plates move apart, capturing the Earth's magnetic field direction at the time of formation.