Unit Test: OpenSciEd 6.4 Plate Tectonics

Question 1

What is a tectonic plate?

Accepted Answer

A large piece of Earth's outer rock layer that moves slowly

Question 2

Scientists recorded the average yearly height change of Mount Everest using GPS stations. Which conclusion is BEST supported by the data?

Accepted Answer

Everest rises slowly but can drop suddenly

Question 3

Scientists drilled into the seafloor at different distances from the Mid-Atlantic Ridge and measured the age of the oceanic rock. Figure: Seafloor Rock Age vs. Distance from Mid-Atlantic Ridge — Line graph showing rock age increasing from 0 million years at the ridge to about 80 million years at 1,600 km from the ridge. — 0: 0 · 400: 20 · 800: 40 · 1200: 60 · 1600: 80 What does this pattern provide evidence for?

Accepted Answer

New rock forms at the ridge and moves outward

Question 4

Students compared data from three locations. Which explanation BEST accounts for why the Andes have volcanoes but the Himalayas do not?

Accepted Answer

At the Andes, a denser oceanic plate sinks under a continental plate and helps form magma

Question 5

A student claims: "South America and Africa were once joined together." The student gathered evidence from the matching coastlines of both continents. Which reasoning uses ALL of the evidence to BEST support the claim?

Accepted Answer

The matching shapes, rocks, and fossils show past connection, and the young seafloor shows how they separated

Question 6

Scientists recorded where earthquakes happened around the world over many years. Use the table below. Statement: The data support the idea that most earthquakes happen along the edges of tectonic plates instead of in the middle of plates.

Accepted Answer

true

Question 7

Scientists measured the age of seafloor rock at different distances from the Mid-Atlantic Ridge. Figure: Seafloor Rock Age vs. Distance from the Mid-Atlantic Ridge — Bar graph showing seafloor rock age rising from 0 million years at the ridge to 80 million years at 2,000 km from the ridge. — 0 km: 0 · 500 km: 20 · 1,000 km: 40 · 1,500 km: 60 · 2,000 km: 80 Statement: The graph shows that the oldest seafloor rock is found closest to the Mid-Atlantic Ridge.

Accepted Answer

false

Question 8

Mount Everest grows about 4 mm taller each year as the Indian Plate pushes into the Eurasian Plate. Scientists also found fossils of ocean animals in rock near the top of the mountain.

Statement: Together, these pieces of evidence suggest that rock once under the ocean was slowly pushed up over millions of years by colliding plates.

Accepted Answer

true

Question 9

Scientists measure the height of Mount Everest over time. Use the table below to answer the question. (a) Describe the overall pattern in Mount Everest's height from 1955 to 2020. (b) Name the type of plate interaction that causes Mount Everest to grow taller. (c) Name ONE other process that could make a mountain shorter.

Accepted Answer

(a) Mount Everest's height increased from 8,848.00 m in 1955 to 8,848.86 m in 2020, so it got about 0.86 m taller. (b) It grows because two continental plates, the Indian Plate and the Eurasian Plate, are colliding (converging). This pushes rock upward (uplift). (c) Weathering and erosion by ice, wind, and water can wear rock away and make a mountain shorter. A large earthquake can also make part of a mountain drop.

Question 10

Figure: Earthquakes per Year (Magnitude 4+) — Bar graph of yearly earthquakes (magnitude 4 or greater): Himalayas 410, Central Canada 6, Andes Mountains 520, Central Australia 9. — Himalayas: 410 · Central Canada: 6 · Andes Mountains: 520 · Central Australia: 9 A class counted earthquakes in four regions. Two regions are along plate boundaries and two are in the middle of plates. (a) Which TWO regions are most likely along plate boundaries? (b) Explain how the earthquake data supports your answer. (c) Explain why earthquakes happen more often at plate boundaries.

Accepted Answer

(a) The Himalayas and the Andes Mountains are most likely along plate boundaries. (b) They have many earthquakes each year (410 and 520). Central Canada and Central Australia have very few (6 and 9). (c) Plates push, pull, or slide against each other at boundaries. Stress builds up in the rock until it breaks or slips along a fault, which releases energy as an earthquake. The middle of a plate moves as one piece, so less rock breaks there.

Question 11

Scientists drilled into the seafloor at different distances from the Mid-Atlantic Ridge and measured how old the oceanic rock was. (a) Describe the pattern in rock age as you move away from the ridge on both sides. (b) Use this pattern to explain what is happening to the plates at the Mid-Atlantic Ridge. (c) Explain where the new rock comes from.

Accepted Answer

(a) The rock is youngest (0 million years) at the ridge and gets older the farther you go. The pattern is almost the same on both sides, reaching about 60 to 62 million years at 1,500 km. (b) This pattern means the plates are moving apart (diverging). New rock forms at the ridge, and older rock is carried away on both sides like two conveyor belts. (c) Magma rises from below where the plates separate. It cools and hardens into new oceanic rock at the ridge, the same process seen in Iceland.

Question 12

Figure: Simplified world map showing three locations marked with stars: (1) the Himalayas, where the Indian and Eurasian continental plates meet; (2) the west coast of South America, where the oceanic Nazca Plate meets the continental South American Plate, with a deep ocean trench offshore and a line of volcanoes in the Andes; (3) Iceland, sitting on the Mid-Atlantic Ridge between the North American and Eurasian Plates. Arrows show plate motion directions at each location. A classmate claims, "All plate boundaries change Earth's surface in the same way." Use evidence from the map and table to argue against this claim. Compare how plate interactions change the surface at ALL THREE locations. In your answer, explain why the Andes have many volcanoes but the Himalayas have few.

Accepted Answer

The claim is incorrect because each boundary changes the surface differently. In the Himalayas, two continental plates collide. Neither plate sinks easily, so the crust crumples and is pushed upward, building tall mountains with few volcanoes and very old rock. In the Andes, the denser oceanic Nazca Plate moves beneath the continental South American Plate (subduction). As the oceanic plate sinks, rock melts into magma that rises and erupts, building volcanoes and adding new volcanic rock. This is why the Andes have many volcanoes and the Himalayas have few: the Himalayas have no sinking oceanic plate to make magma. In Iceland, the plates move apart. Magma rises to fill the gap and forms very young new oceanic rock. All three locations have earthquakes, but they build or change land in different ways: crumpling, volcanic building, and spreading.

Question 13

Describe the three ways that tectonic plates can interact at a plate boundary. For EACH type of interaction, name ONE landform or event that can happen there.

Accepted Answer

Tectonic plates can interact in three ways. First, when plates collide (converge), the rock is pushed up, forming mountains like the Himalayas, or one plate can go under another and form volcanoes. Second, when plates separate (diverge), magma rises and forms new oceanic rock, like at the Mid-Atlantic Ridge in Iceland. Third, when plates slide past each other, they get stuck and then slip suddenly, causing earthquakes, like along the San Andreas Fault.

Question 14

Scientists measured the height of Mount Everest using GPS over several years. Use the data table below to answer the question. Describe the pattern in the data. Then explain what is happening below Earth's surface that causes Mount Everest to change in this way.

Accepted Answer

The data show that Mount Everest is getting taller by about 4 to 5 mm every year and is moving northeast each year. This is happening because the Indian Plate is moving north and colliding with the Eurasian Plate. Neither plate sinks easily because both are made of continental rock, so the rock crumples and is pushed upward. This uplift slowly makes Everest taller, and because the plate keeps moving, the mountain also shifts its location.

Question 15

A student compared two types of rock found in Earth's crust. Use the data table below to answer the question. When an oceanic plate and a continental plate collide, which plate moves beneath the other? Use evidence from the table to explain your answer, and describe ONE landform that forms as a result.

Accepted Answer

When an oceanic plate and a continental plate collide, the oceanic plate moves beneath because it is denser. The table shows oceanic rock has a density of 3.0 g/cm³ while continental rock is only 2.7 g/cm³, so the oceanic plate sinks under the lighter continental plate. As the oceanic plate goes deep underground, heat and pressure melt rock into magma, which rises and erupts to form a chain of volcanoes, like the Andes Mountains. This also explains why oceanic rock is much younger: it gets recycled back into Earth.

Question 16

Scientists collected the age of seafloor rock at different distances from the Mid-Atlantic Ridge near Iceland. Figure: Seafloor Rock Age vs. Distance from Mid-Atlantic Ridge — Line graph showing seafloor rock age increasing from 0 million years at the ridge to 80 million years at 1,600 km from the ridge. — 0: 0 · 400: 20 · 800: 40 · 1200: 60 · 1600: 80 Describe the pattern shown in the graph. Then explain how this pattern is evidence that the plates on either side of the ridge are moving apart.

Accepted Answer

The graph shows that as distance from the ridge increases, the rock gets older. Rock at the ridge is 0 million years old, and rock 1,600 km away is 80 million years old. This is evidence that the plates are moving apart because new oceanic rock forms at the ridge when magma rises up through the gap and cools. As the plates keep separating, that rock is carried away from the ridge and newer rock forms behind it. So the youngest rock is in the middle and the oldest is farthest away, like a conveyor belt. If the plates were not moving, the rock would not show this pattern.

Question 17

Use the data table below, which shows information collected about three regions, to answer the question. Decide which region(s) are located at or near a plate boundary and identify the type of boundary for each. Support your claim with at least TWO pieces of evidence from the table, and explain why the remaining region is likely NOT near a plate boundary.

Accepted Answer

I claim that the Himalayas and the Andes are near plate boundaries. My evidence is that both regions have many earthquakes (120 and 150 per year) and very high mountains (8,849 m and 6,961 m), which form when plates collide and rock is uplifted. The Himalayas have no volcanoes and no trench, so this is likely a collision between two continental plates, where neither plate sinks. The Andes have over 40 active volcanoes and a deep ocean trench, which shows an oceanic plate moving beneath a continental plate; the sinking plate melts and forms magma that feeds the volcanoes. The region that is not near a boundary is Central Kansas because it has only about 1 earthquake per year, no volcanoes, and flat plains. This suggests it is in the middle of a plate where the rock is not being pushed, pulled, or melted by plate interactions.

Question 18

Scientists recorded the location of earthquakes in one year. Use the table to answer. Because most earthquakes happen in long lines near mountains and ridges, scientists use these patterns to locate the edges of tectonic plates, called _____.

Accepted Answer

plate boundaries

Question 19

Students measured the age of seafloor rock at different distances from the Mid-Atlantic Ridge. Figure: Seafloor Rock Age vs. Distance from Mid-Atlantic Ridge — Line graph showing seafloor rock age increasing from 0 million years at the ridge to 60 million years at 1,200 kilometers from the ridge. — 0: 0 · 200: 10 · 400: 20 · 600: 30 · 800: 40 · 1000: 50 · 1200: 60 The rock is youngest at the ridge and gets older farther away, which is evidence that the plates are moving apart at a type of boundary called _____.

Accepted Answer

divergent

Question 20

Along the west coast of South America, a dense oceanic plate collides with a less dense continental plate. This produces deep earthquakes, a chain of volcanoes, and rising mountains. These features are best explained by the oceanic plate sinking beneath the continental plate in a process called _____.

Accepted Answer

subduction

Time Period	Total Height Change (mm)
2000–2005	+20
2005–2010	+20
2010–2015	+20
2015 (Nepal earthquake)	−25
2015–2020	+20

Unit Test: OpenSciEd 6.4 Plate Tectonics

Part A: Multiple Choice

Part B: True / False

Part C: Short Answer

Part D: Essay / Extended Response

Part E: Fill in the Blank

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