Earth's Layers — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
The oceanic crust is thicker than the continental crust and made of granite.
Corrected: The oceanic crust is thinner than the continental crust and made of basalt.
The corrected sentence is: "The oceanic crust is thinner than the continental crust and made of basalt.". The original sentence "The oceanic crust is thicker than the continental crust and made of granite." contained an error that needed to be fixed.
2. Fix the sentence:
The outer core is a solid layer made of rocks and minerals.
Corrected: The outer core is a liquid layer made of molten iron and nickel.
The corrected sentence is: "The outer core is a liquid layer made of molten iron and nickel.". The original sentence "The outer core is a solid layer made of rocks and minerals." contained an error that needed to be fixed.
3. Fix the sentence:
The mantle is completely solid and never moves at all.
Corrected: The mantle is made of hot rock that can flow very slowly over long periods of time.
The corrected sentence is: "The mantle is made of hot rock that can flow very slowly over long periods of time.". The original sentence "The mantle is completely solid and never moves at all." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Continental crust is about 30 to 50 kilometers thick and made mostly of granite.
Continental crust (land masses) is made primarily of granite, a less dense igneous rock.
2. Oceanic crust is thinner and denser than continental crust and made mostly of basalt.
Oceanic crust (ocean floors) is made primarily of basalt, a denser igneous rock.
3. The temperature of the inner core reaches about 5,000 degrees Celsius.
The inner core temperature approaches that of the Sun's surface — about 5,000°C.
4. Both the outer core and inner core are made of iron and nickel.
Both core layers consist primarily of iron and nickel, with the outer being liquid and inner being solid.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. How are the outer core and inner core similar, and how are they different?
Sample answer: Both the outer core and inner core are made of iron and nickel. However, the outer core is liquid because there is less pressure, while the inner core is solid because the immense pressure keeps it packed tightly together.
Composition is the same, but state of matter differs due to pressure differences.
2. Why is the mantle considered the thickest layer of Earth?
Sample answer: The mantle is about 2,900 kilometers thick, which is much greater than the crust, outer core, or inner core. It makes up most of Earth's volume and sits between the thin crust above and the core below.
Crust ≈ 35 km, outer core ≈ 2,200 km, inner core ≈ 1,200 km, but mantle ≈ 2,900 km — the thickest.