Earth’s InteriorConcept 2 Notes

How do Geologists Learn about Earth’s Interior?

• Geologist – someone who studies Earth’s rocks, structures, and landmasses

• Unable to see deep inside of Earth• Deepest attempt was in 2011

• Into a previously started drill site 2km into the ocean crust. (Ocean crust is thinner.) Its goal was to sample the lower crust of Earth. Read the article here: http://www.bbc.co.uk/news/science-environment-12841150

• 2 types of evidence to learn about the interior – • Direct• Indirect

Rock Sample Evidence

• Direct Method

• Geologists have drilled 12.3 km (7.64 mi) into Earth’s crust (continental plate)

• Volcanoes shoot out rocks from inside of Earth

• Re-create early conditions of Earth in laboratory to see what original rocks may have been like.

Evidence from Seismic Waves

• Indirect Method

• Earthquakes create

• Speed and path of seismic waves give geologist clues about the interior of Earth’s structure.

Features of Earth’s Interior Layers

• Interior Layers are: Crust, Mantle, Core

• The layers are different, but there are some rules that apply as you travel closer to the center of the Earth.• The deeper down into Earth you go, the

higher the pressure. This is due to the weight of the layers of rock above each other.

• The temperature inside of Earth increases as depth increases. Rock starts out cool near Earth’s surface, after 20 meters the rock is warmer, every 40 meters after that there is an increase in temperature by 1° C.

Features … (Cont.)

• Eventually the temperatures increase more slowly.

• The temperature increase or HEAT is due to the pressure and some of the leftover heat from the formation of Earth – 4.6 billion years ago. (Heat is trapped inside.)• Read me:

http://news.sciencemag.org/sciencenow/2011/07/earth-still-retains-much-of-its-.html

The Crust

• Rock layer that forms Earth’s outer “skin”

• Solid rock that includes both dry land and the ocean floor.

• Main elements it contains are: oxygen and silicon

• 5-40 Km thick • thickest under high mountains (80 km !)• thinnest beneath oceans

• Overall, the crust is the thinnest layer of Earth’s interior.

Oceanic Crust

• Under ocean

• Mostly composed of the rock, basalt, which is dark and fine-grained.

Continental Crust

• Forms the continents

• Contains many types of rocks, but overall it is much like granite, which is light in color and has coarse grains.

• Both granite and basalt have more O and Si than any other elements.

The Mantle

• Layer of hot rock

• 3,000 km thick

• Divided into three parts based on their physical characteristics• Lithosphere• Asthenosphere• Mesosphere

Lithosphere

• Uppermost part made of brittle (easy to break) rock

• Strong, hard, rigid

• Grouping the crust and the uppermost mantle together you get the lithosphere = 100 km thick

Asthenosphere

• Hotter material under increasing pressure

• Can bend (like metal)

• Still solid

Mesosphere

• Hot but more rigid than the asthenosphere

• Stiff due to increasing pressure.

• Includes the transitional zone which is just below the asthen.

• Includes lower mantle that extends into Earth’s core.

The Core

• Made of mostly iron and nickel with 2 parts.

• Outer Core (liquid) – layer of molten metal surrounding the inner core.• 2,258 km thick

• Inner Core (solid but molten)– Dense ball of solid metal due to the extremely intense pressure in the inner core, iron and nickel atoms cannot spread out enough to become solids.• 1,222 km thick

• There is some data to suggest that along with the metals, there is oxygen, sulfur and silicon.

Seeing the layers differently…

• YOU DO NOT HAVE TO WRITE THIS SLIDE. YOU DO HAVE TO USE THE WEBSITE!!!

• Check out this site: http://www.learner.org/interactives/dynamicearth/structure.html

• Explore it. Play with it. It will reinforce the notes you have taken and help you to better understand what you have read and written.

The Core and Earth’s Magnetic Field

• Thought that movement of liquid of outer core created Earth’s magnetic field

• Earth acts like a giant bar magnet and has a magnetic field.

• It affects the whole planet.

• This is the reason that compasses work here on Earth (magnetic).

• http://adventure.howstuffworks.com/outdoor-activities/hiking/compass1.htm• View this to BETTER understand this concept of

Earth’s magnetism.

Convection in the Mantle

• How is heat transferred?• Radiation – sun transfers light and heat through

the air warming the objects on Earth. Transfer of energy through waves is radiation.

• Convection – heat transferred by movement of a fluid. Happens in air and water. Hot air or water rises and cold air or water falls.

• Conduction – heat transferred between things that are touching. (Direct contact such as your feet on the hot pavement in summertime.)

Convection Currents

• As air or plain liquids get hot, they expand. This makes them less dense. (DENSITY is how much mass there is in an a given amount of volume for a substance.) The warm, less dense soup rises, and the cooler, denser soup sinks towards the bottom. (Gravity is responsible for this sinking. Denser objects sink in less dense objects.)

• This begins a constant flow called convection current.

• A heat source is needed to keep this working.

Convection Currents in the Mantle

• Large amounts of heat are transferred by convection currents within the core and mantle.

• Heat from the core and mantle cause the convection currents in the mantle.

• How does mantle rock flow?• Very slowly from the bottom to the top• This process has been happening for more than

4 billion years!

Convection Currents in Outer Core

• Here, the currents cause Earth’s magnetic field.