BELLWORK: HOW DO GEOLOGISTS LEARN ABOUT EARTH’S INTERIOR?

CH. 3, LESSON 1: EARTH’S INTERIOR

Processes on the Earth’s surface are often a result of what’s going on inside the Earth. Although geologists are unable to see deep inside the Earth, they are able to use other methods to study beneath it’s surface. 2 Main types of evidence to learn about the Earth’s interior: –Analysis of rock samples (Direct Evidence) –Seismic waves (Indirect Evidence)

ROCK SAMPLES Geologists use drills to dig beneath the Earth’s surface. When drilling, geologists are able to bring up rock samples Rock samples give clues to the Earth’s structure and conditions inside the Earth, where the rocks were formed. Volcanoes sometimes blast rocks above the surface from depths of more than 100 km. These rocks can provide more information about our Earth’s interior.

ROCK SAMPLES In studying rock samples, Geologists have been known to re-create our planet’s interior conditions within laboratories, and see how they behave under such conditions:  Laser beams - focused on the rock, while creating pressure on it with great force

SEISMIC WAVES When you toss a pebble into a pond, it creates radiating waves in the water. An earthquake does the same thing with energy. Earthquakes produce seismic waves which can be studied and analyzed in how far it travels through or over the Earth. The speed and paths of the seismic wave can give clues about our planet’s interior structure The path of ocean waves when they reach an island

LAYERS OF THE EARTH Three main layers of the Earth  Crust  Mantle  Core Each layer is different by its size, composition, temperature and pressure Pressure – the deeper inside Earth you go, the more pressure you will find Temperature – increases as the deeper inside the Earth you go.

EARTH’S CRUST Layer of solid rock that forms the Earth’s outer skin It is the thinnest layer and is typically between 5 – 40 km thick Two types: –Continental crust (forms and lies beneath dry land) –Oceanic crust (forms and lies beneath the ocean floor) The oceanic crust is made up of Basalt (dark, fined-grained rock) & ocean sediment. The continental crust composition, however, varies more. It contains several types of rocks. Overall it resembles Granite (light color and coarse-grains) Both Granite and Basalt have more oxygen and silicon than any other element

EARTH’S CRUST The composition of the Earth’s crust

THE MANTLE About 40 km below the Earth’s surface, this layer of rock contains more Iron and Magnesium than found in the crust. This layer of rock is very hot, yet solid The mantle is nearly 3,000 km thick The mantle is divided into layers based on physical characteristics –Lithosphere (avg. 100km) - most similar to the crust. It is hard, strong and rigid. –Asthenosphere – less rigid than Lithosphere, hotter and under more pressure. –Mesosphere – hot but more rigid than layer on top. This increased stiffness is due to the pressure placed on this layer. The mesosphere includes a region called the transition zone, which lies beneath the asthenosphere.

THE MANTLE

THE CORE Mostly made up of the metals Iron and Nickel, but some evidence has emerged which suggests the core contains oxygen, sulfur and silicon. Two Parts –Outer Core (dense liquid) – Molten metal surrounding the inner core –Inner Core (dense solid) – extreme pressure squeezes the atoms of iron and nickel so much that the atoms cannot spread out to become liquid.

THE CORE Where do these terms go on the Venn diagram?

THE CORE The graph shows how temperatures change between Earth’s surface and the core.

THE CORE AND THE EARTH’S MAGNETIC FIELD Due to the movements in the liquid outer core, some scientists think that the Earth’s magnetic field is created in the process. The Earth’s magnetic field has a north and south pole, like the magnetic field at each end of a bar magnet. When you use a compass, the compass needle aligns with the lines of force in Earth’s magnetic poles. So the needle points to the Earth magnetic north pole, Not the Earth’s geographic location. North Pole