Earth's Crust - Definition, Examples, Quiz, FAQ, Trivia
Discover the thin outer layer that forms the surface of our planet!
What is Earth's Crust?
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Earth's crust is the thin, solid outer layer of our planet that we live on. It's like the skin of an apple - thin compared to the rest of the Earth but essential for life!
The crust makes up less than 1% of Earth's total volume but forms all of the continents and ocean floors. It ranges from about 5-70 km (3-44 miles) thick. The continental crust is thicker but less dense, while the oceanic crust is thinner but denser.
Crust Fact!
If Earth were the size of a basketball, the crust would be thinner than a piece of paper!
Types of Earth's Crust
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There are two main types of Earth's crust, each with different characteristics:
Continental Crust
Forms the continents and continental shelves
Thickness: 30-70 km
Composition: Mostly granite
Oceanic Crust
Forms the ocean floors
Thickness: 5-10 km
Composition: Mostly basalt
The continental crust is thicker but less dense, which is why continents "float" higher on the mantle than the denser oceanic crust. The oceanic crust is constantly being created at mid-ocean ridges and destroyed at subduction zones.
The Crust and the Mantle
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The crust doesn't exist alone - it's part of Earth's outer layers:
Crust
The solid outer layer we live on
Lithosphere
Crust + rigid upper mantle (100 km thick)
Asthenosphere
Semi-fluid layer beneath the lithosphere
The lithosphere (which includes the crust) is broken into large pieces called tectonic plates. These plates "float" on the semi-fluid asthenosphere below and slowly move over time. This movement causes earthquakes, volcanoes, and the formation of mountains.
Plate Movement!
Tectonic plates move about as fast as your fingernails grow - 2-5 cm per year!
Earth's Crust Quiz
Test your knowledge about Earth's crust with this quiz! Answer all 5 questions to see how much you've learned.
Frequently Asked Questions
Here are answers to common questions about Earth's crust:
Earth Crust Trivia
Discover some amazing facts about Earth's crust!
Thickness Variation
The crust is thinnest under oceans (about 5 km) and thickest under mountains (up to 70 km under the Himalayas).
Ocean Floor Recycling
The entire ocean floor is recycled every 200 million years! That's why oceanic crust is much younger than continental crust.
Deep Heat
Temperature increases as you go deeper into the crust - about 25-30°C per kilometer! At 12 km deep, temperatures reach over 180°C (356°F).
Mineral Wealth
Nearly all minerals used by humans come from Earth's crust. The most abundant elements are oxygen (47%), silicon (28%), and aluminum (8%).
