Earth Structures: Layers, Rocks, Minerals, and Plate Tectonics

Lesson Overview

• What's Inside the Earth?
• What Are Rocks Made Of?
• How Do Rocks Change?
• What Are Minerals?
• How Do Weathering and Erosion Shape Earth?
• What Causes Plate Tectonics?
• Why Do Plates Move?
• What Happens to Rocks Under Pressure?

Have you ever wondered what's hidden deep beneath your feet, far below the surface of the Earth? In this lesson, you'll explore the amazing structures that make up our planet. You'll learn about Earth's internal layers, crust, mantle, and core, and the unique rocks and minerals that form the surface we walk on. We'll also discover how massive plates of Earth's crust slowly move, causing earthquakes, volcanic eruptions, and mountain formation. 

What's Inside the Earth?

Imagine slicing the Earth open like cutting through a juicy peach. You would see various layers, each composed of distinct materials that play unique roles in our planet's structure. Scientists categorize Earth into three primary layers based on their chemical compositions:

Crust is Earth's thin, rocky outer shell, providing the surface on which we live. Despite being solid and sturdy beneath our feet, the crust is incredibly thin compared to the deeper layers.

Mantle is a thick, hot layer of semi-solid rock situated beneath the crust. It flows very slowly, much like thick caramel, due to immense heat and pressure.

Core lies at Earth's deepest point and consists primarily of iron and nickel. It is incredibly hot and dense, with temperatures comparable to the surface of the Sun!

Quick Fact: Think of Earth's crust as similar to the thin skin of an apple-remarkably slender when compared to what's beneath.

What Are Rocks Made Of?

Earth's crust is constructed from different types of rocks. Each rock carries a unique story about Earth's past.

Types of Rocks:

The primary differences between rocks depend on how they are formed:

1. Igneous rocks develop when magma or lava cools and solidifies. Examples include granite and basalt.
2. Sedimentary rocks form when layers of sediment accumulate and compress over time. Common examples are sandstone and shale.
3. Metamorphic rocks originate from existing rocks that transform under immense heat and pressure, resulting in new rock types such as marble and gneiss.

Did You Know? Through weathering and erosion, all rock types eventually break down into smaller pieces called sediments.

How Do Rocks Change?

Rocks are continuously changing through the Rock Cycle, an ongoing process illustrating how one type of rock transforms into another.

Example: Granite, an igneous rock, can become gneiss, a metamorphic rock when subjected to intense heat and pressure deep within Earth.

What Are Minerals?

Rocks are composed of minerals, similar to how recipes combine ingredients like flour and sugar to create delicious treats.

What Defines a Mineral?

A mineral must satisfy these requirements:

• It must form naturally (not man-made).
• It must be inorganic (never living).
• It must have a crystalline structure with atoms arranged in orderly patterns.

Silicate Minerals:

Many minerals within rocks belong to the silicate family, compounds primarily made from silicon and oxygen atoms.

Identifying Minerals:

Geologists often perform tests to identify minerals. One common test is the streak test, where minerals are scratched across a porcelain plate to observe the color of their powder.

How Do Weathering and Erosion Shape Earth?

Weathering:

Weathering occurs when rocks break into smaller fragments due to temperature fluctuations, water, wind, and other natural forces.

Example: Cracks forming in sidewalks represent the effects of weathering.

Erosion:

Erosion is the movement of weathered rock particles by natural forces such as water, wind, or ice.

Example: Glaciers scrape the ground, breaking rock into smaller particles-a process of weathering. Transporting these particles away from their original location is erosion.

What Causes Plate Tectonics?

Earth's crust consists of giant puzzle pieces called tectonic plates. These plates continually shift due to heat-driven movements within Earth's mantle called convection currents.

Types of Plate Boundaries:

• Divergent boundaries occur where plates move apart, creating new crust (example: Mid-Atlantic Ridge).
• Convergent boundaries happen when plates collide, forming mountains like the Rocky Mountains.
• Transform boundaries exist where plates slide horizontally past one another, such as California's San Andreas Fault.

Example: Earthquakes frequently occur along transform boundaries due to sliding tectonic plates, as witnessed in California.

Did You Know? Continental Drift theory proposes that continents were once joined as a supercontinent and have slowly drifted apart.

Why Do Plates Move?

The heat from Earth's core creates currents within the mantle, causing hot material to rise and cooler material to sink. This cycle of movement, known as convection currents, drives tectonic plates to move.

Example: Heating soup causes circulation, similar to how convection currents operate deep within Earth.

What Happens to Rocks Under Pressure?

When rocks experience intense pressure deep beneath the Earth's surface, they undergo metamorphism, transforming into entirely new rock types.

Ask Yourself: Imagine sedimentary rocks on the ocean floor being buried deep inside Earth. What might they become?

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Earth Structures Retake Test-Part One