The Mystery at Earth's Center

The Earth's crust…

• has a strong smell.

• is hotter than the sun.

• is thousands of miles deep.

• has been opened with powerful bombs.

Earthquakes help scientists understand…(Easy)

• how much damage happens on Earth's surface.

• the temperature of the Earth's center.

• the way Earth's center looks.

• how to open Earth's surface.

Today scientists… (Easy)

• are done studying the Earth's core.

• believe the Earth's core is no longer changing.

• have new questions about the Earth's core.

• think the inner core and outer core are the same.

What is the main idea of the text? (Hard)

• It is difficult for humans to study the Earth's core, but scientists use earthquake waves to learn more.

• The Earth's center was puzzling for scientists for many years until they were able to drill deep into its surface.

• There are many places in the world left to explore and one of the most fascinating places to study is the Earth's center.

• Scientists think that starting small earthquakes and recording where their waves go could help us learn more about the Earth's core.

Which detail best shows why studying the Earth's center is difficult? (Medium)

• "Not only is Earth's core far, far down, but as the layers go deeper, they also grow hotter." (Paragraph 4)

• "Earth's crust is made up of gigantic plates that move very slowly." (Paragraph 6)

• "The inner core is almost as big as the moon, and it's mostly made of iron. " (Paragraph 9)

• "New research hints there might be something else at the deepest part of Earth's center." (Paragraph 10)

Which sentence best explains how the Earth's mantle is different from the Earth's inner core? (Medium)

• The mantle is deeper beneath the Earth's surface than the inner core.

• The mantle is a hotter temperature than the inner core's temperature.

• The mantle is made of liquid rock and the inner core is made of solid iron.

• The mantle is a mystery to scientists but they know everything about the inner core.

The word "expand" in paragraph 10 most closely means —(medium)

• to speed up.

• to get looser.

• to be hidden.

• to become larger.