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 mantle is the thinnest layer of Earth and we live on top of it.
Corrected: The crust is the thinnest layer of Earth and we live on top of it.
The corrected sentence is: "The crust is the thinnest layer of Earth and we live on top of it.". The original sentence "The mantle is the thinnest layer of Earth and we live on top of it." contained an error that needed to be fixed.
2. Fix the sentence:
Earth has three layers called the crust, mantle, and core.
Corrected: Earth has four layers called the crust, mantle, outer core, and inner core.
The corrected sentence is: "Earth has four layers called the crust, mantle, outer core, and inner core.". The original sentence "Earth has three layers called the crust, mantle, and core." contained an error that needed to be fixed.
3. Fix the sentence:
The inner core is made of liquid iron and nickel that flows freely.
Corrected: The inner core is made of solid iron and nickel held together by immense pressure.
The corrected sentence is: "The inner core is made of solid iron and nickel held together by immense pressure.". The original sentence "The inner core is made of liquid iron and nickel that flows freely." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. The crust is the outermost layer of Earth where people, animals, and plants live.
The crust is Earth's thin outer shell where all life exists.
2. The mantle is the thickest layer of Earth at about 2,900 kilometers deep.
The mantle extends about 2,900 km deep and is Earth's thickest layer.
3. The outer core is a liquid layer made of melted iron and nickel.
The outer core is molten (liquid) metal. This is proven by seismic wave behavior.
4. The inner core is solid even though it is extremely hot because of enormous pressure.
Intense pressure squeezes the iron and nickel in the inner core into a solid state.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. List Earth's four layers in order from the surface to the center.
Sample answer: The four layers from surface to center are the crust, the mantle, the outer core, and the inner core.
Earth's layers from outermost to innermost: crust → mantle → outer core → inner core.
2. Why is the crust important for life on Earth?
Sample answer: The crust is important because it is the solid outer layer where all living things exist. It provides the land and ocean floors that support habitats for plants, animals, and people.
All known life lives on or near the crust. Without it, life as we know it would not be possible.