Section 1-1 Earth’s Interior

Objectives F.1.1.1. Explain how Geologists learn about Earth’s interior structure. F.1.1.2. Identify characteristics of Earth’s crust, mantle and core.

Exploring Inside Earth Geologists use two types of evidence to study Earth’s interior: direct evidence from rock samples and indirect evidence from seismic waves. Objective F.1.1.1.

Rock Samples-How Are These Different?

What Are Some Things We Can Learn From Rocks? Earth’s chemical composition. The interrelated processes that take place on Earth. Some structure and density. Volcanic eruptions, mountain building, weathering, erosion and even earthquakes all involve rocks and minerals. Some minerals are quite valuable.

Sampling A Volcano

Evidence From Seismic Waves After an earthquake, seismic waves travel through Earth and reveal information about the internal structure of the planet.

Earth’s Layers The three main layers of Earth are the crust, mantle and the core. Objective F.1.1.2.

Earth’s Layers

Pressure And Temperature As you descend deeper into the Earth, what happens to pressure and temperature? They both increase to thousands of degrees and millions of tons of pressure.

Different Densities Differences in density will cause things to separate into layers. Where does the “lighter” stuff go? It floats on top. Where does the heavier stuff go? It sinks to the bottom.

Earth’s Crust The crust is a layer of solid rock that covers the entire planet and includes land and ocean floor. Objective F.1.1.3. Think of ocean floor as land that is just covered by water.

Earth’s Crust Earth’s crust is divided into two categories: Oceanic and Continental. Oceanic Crust is made of Basalts that are dark and fine texture. Continental Crust is made of Granite which is often lighter in color and has a coarser texture.

Basalts/Oceanic Crust

Granite/Continental Crust

Where Else Have We Seen Basaltic Lava Flows

Earth’s Mantle Earth’s mantle is made up of rock that is very hot but still solid. Geologists divide the mantle into layers based on physical characteristics. Overall, the mantle is around 1,800 miles thick. Objective F.1.1.3.

Earth’s Mantle/Lithosphere The lithosphere is the uppermost rigid layer of the mantle that includes the top of the mantle and the crust. It’s about 60 miles thick.

The Lithosphere Lithos is Greek for Rock. So the lithosphere is the “rock” sphere of the planet. It is made of the crust and the uppermost, solid part of the mantle.

Earth’s Mantle/Asthenosphere The asthenosphere is the next layer down. It’s much hotter and while it can slowly flow and bend it is still considered a solid. Pressure keeps it in solid form.

The Asthenosphere Just below the lithosphere is the asthenosphere. It is a layer of solid rock that is very hot, flows very slowly and carries the tectonic plates along with it.

Earth’s Lower Mantle The lower mantle extends all the way down to core. Do you know what causes the Earth to “layer” itself? Different Densities

Earth’s Core Earth’s core is made of the elements iron, nickel and cobalt. Why did these elements sink to the center of Earth? Because they are the most dense!

Earth’s Outer and Inner Core How Are They The Same? How Are They Different? Made of the same metals: Iron and Nickel. The outer core is liquid. The inner core is solid

Earth’s Core What squeezes the inner core so much that it becomes a solid. Pressure from: Gravity

Earth’s Magnetic Field Geologists believe Earth’s magnetic field is caused by the movement of liquid in Earth’s outer core. One thing we know for certain is that the magnetic field is essential for life on Earth. It protects the planet from the hostile environment of space.

Earth’s Magnetic Field

Section 1-1 Assessment 1a. Why is it difficult to determine Earth’s inner structure? Because Earth is thousands of miles in diameter and we can only drill a few miles deep into the crust. Therefore we must use indirect methods to learn about Earth’s interior. 1b. How are seismic waves used to provide evidence about Earth’s interior? Different types of seismic waves travel through different layers of Earth at different speeds and when the waves are recorded after an earthquake they carry information with them.

Section 1-1 Assessment 2a. List Earth’s three main layers. Crust-Mantle-Core 2b. What is the difference between the lithosphere and the asthenosphere and where is each layer located? The lithosphere is the top layer and it is rigid. The asthenosphere is below the lithosphere and it’s hotter and under more pressure so it’s more plastic.

Section 1-1 Assessment 2c. Classify these layers. Lithosphere Solid Asthenoshpere Solid but can flow slowly

Section 1-1 Assessment Lower Mantle Solid but can flow slowly Outer Core Liquid Inner Core Solid