The Earth’s Interior

THE Earth is made of 4 layers

Important note Layers do not have a uniform or “perfect” boundary. Example- Earths crust is as small as 5 km in some places and as deep as 70 km in others.

The Crust

The crust It is the thinnest and outer most layer that makes up planet Earth. It goes from the ground we stand on to about 40 km down ( on average). Earths crust is comprised of continents and ocean basins.

Two types of crust

Oceanic Crust The oceanic crust is the portion of Earth's crust that makes up the seafloor. It is between 5 to 12 kilometers (3 -8 miles) thick The rocks of the oceanic crust are denser (3.0 g/cm3 ) than the rocks that make up the continents.

Continental crust The continental crust is the portion of Earth's crust that makes up the continents. It is 40 kilometers thick on average, but it varies a lot. It can be much thicker in mountain ranges (70 km). On average, continental crust is much less dense (2.7 g/cm3 ) than oceanic crust. Since it is less dense, it rises higher above the mantle than oceanic crust.

What's Density Scientifically - mass per unit volume. Generally- the amount of mass in a given space. If two objects are the same size and one has a mass of 25g and the other is 40g then the one with the higher mass is more dense. (heavier)

The Mantle The mantle is about 2900 km (1,800 mi) thick, making up about 84% of Earth’s total volume,

The mantle Lithosphere Asthenosphere Includes the crust and the upper most mantle. The lithosphere is about 100 kilometers thick. It is brittle and can break when stressed (earthquakes) The asthenosphere is solid middle mantle material that is so hot that it behaves plastically and can flow. We say it is solid, but bendable. The lithosphere rides on the asthenosphere.

The core

The core Outer core Inner core Liquid Both contain heavy metals (nickel and iron) Both responsible for the magnetic field Solid Both contain heavy metals (nickel and iron) Both responsible for the magnetic field

Why so hot? The first source is heat left over from the formation of the Earth. The next source is gravitational pressure put on the core by tidal forces and the rotation of the Earth. The last known source of heat is the radioactive decay of elements in the inner part of the Earth.

How do we know the composition of the earth? Direct Evidence Indirect Evidence Geologists use direct evidence from rock samples to gather clues about Earth’s structure. Volcanos and lava are also places to gather information The deepest geologists have ever drilled is on the Kola Peninsula in the Soviet Union. They reached 12.26 km (7.5 mi) into the Earth’s crust. This took for years to dig. Geologists record the seismic waves and study how they travel through the Earth. The speed of seismic waves and the paths they take reveal the structure of the planet. The waves travel at different speeds due to changes in density of earths interior

Seismic waves

Heat Transfer

Three types Radiation is energy transferred by electromagnetic waves (or photons). Convection typically arises from the movement of gases or liquids over large distances. Conduction occurs through touch and flows from hot to cold.

Radiation Energy transferred by radiation from the sun travels millions of kilometers through the vacuum of space before reaching the Earth. Some of this energy is visible radiation (sunlight, for example), while other energy is invisible. Heat radiation is an example of invisible radiation. When you sit next to a campfire or a fireplace and feel all warm and cozy, thank radiation! It is the flow of radiation from the fire that warms us.

Convection Convection takes place throughout the Earth’s atmosphere all the time. Heated air is less dense than cooler air, so it rises. As the air rises, it cools down and becomes denser. The air then falls back to the ground where it is heated again, and the process repeats. A convection cell, which is a circulating pattern of moving energy, is now created.

Convection

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Convection in Earth Science Convection takes place in the mantle and is believed to be the cause of our tectonic plates movement over time Within the Earth’s interior, large convection currents in the asthenosphere transfer heat from the core to the surface, where it becomes cooler and more dense. The less dense, hot material rises. Cold, denser material convects downward because of grav- ity and the cycle continues.

Conduction Conduction happens when a temperature difference exists, causing the molecules of an object to transmit energy throughout the object Conduction is the transfer of kinetic energy from one molecule to another by molecular collision. Conduction occurs, for example, when a metal spoon is put into a hot cup of tea and the handle of the spoon gets hot. This means, of course, that you don’t want to grab the handle of a copper (or any metal) pot when it’s being heated on your stove.