Layers of the Earth Layers of the Earth

Layers of the Earth

Layers of the Earth § There are two ways that scientists label the layers of the Earth. § Composition layers § Physical/Mechanical layers

Composition layers

Density § Earth’s layers are characterized by many things, one of which is density. § Density is the relationship between mass and volume § Density = mass/volume § The deeper you move towards the center of the earth, the denser (and hotter) the layer!

Composition layers § These are the more familiar layers. They are: § Crust § Ranges from 5 to 100 km in thickness § Thinnest layer of the Earth § Least dense § Split into two types: Continental and Oceanic § Continental is thicker than oceanic § Mantle § Roughly 2900 km thick – the thickest layer! § No one has ever drilled to the mantle. It is also very hot § Has properties of a liquid and a solid (it is plastic)

§ Core § Mostly made of iron and nickel § Outer core: liquid, very dense § Inner core: solid from pressure § temperatures and pressures so great the metals are squeezed together and are not able to move § The core’s diameter is roughly 6856 km (about the size of Mars)

Physical Layers

Physical Layers § The less familiar layers are the physical layers. They are based on how the layer looks or acts. § Lithosphere “rock sphere” (15 -300 km) § The tectonic plates § A combination of crust and the upper region of the mantle § Cold and brittle (easily broken) § Asthenosphere “weak sphere” (250 km) § Hard rock that acts like warm tar or honey (plastic) § Has properties of a liquid AND a solid § What the tectonic plates float on § HOT

Physical layers 2 § Mesosphere “middle sphere” (2550 km) § Rest of the mantle § Much stronger and hotter than the Asthenosphere § Outer Core (2200 km) § Liquid layer § Inner Core (diameter= 2456 km) § Solid, dense core of the planet

Interesting fact… § Did you know? . . . § The center of the Earth’s core is hotter than the surface of the sun. The temperature of Earth’s inner core reaches 6000 °C whereas the surface of the sun is roughly 5500 °C. § The sun’s core, however, is 15, 000 °C

Side by side comparison Crust Mantle Lithosphere Asthenosphere Mesosphere Core Outer Core Inner Core

Review 1) What are the four layers of the Earth? 2) The Earth’s crust is very ______? 3) The mantle is the largest layer of the Earth? True or False 4) Is the Outer Core a liquid or a solid?

Answers! 1) Crust, Mantle, Outer Core, Inner Core 2) Thin 3) True 4) Liquid

Plate Tectonics

Theory of Continental Drift § Theory by Alfred Wegener § Continental drift is theory that continents can drift apart from one another and have done so in the past. § Puzzling observations that could be explained by continental drift: § Puzzle-like fit of the continents § Fossils of the same plants and animals found on both sides of the Atlantic Ocean § Strange grooves cut by ancient glaciers that line up

Theory of Seafloor Spreading § Harry Hess was a geologist that studies the ocean floor § He discovered that the sea floor seemed to be pulling apart, and magma came up in the middle § This helps support Continental Drift!

Tectonic Plates § With the idea that continents can drift apart, scientists felt that some force had to be making these continents move. § The theory of plate tectonics developed as a way to explain continental drift

Tectonic Plates § Tectonic plates are large pieces of the lithosphere that move around on top of the asthenosphere like icebergs in the ocean. § There are 10 major plates

When plates collide! § Plate tectonics is theory that the Earth’s lithosphere is divided into large tectonic plates that move around on top of the asthenosphere. § All plates share boundaries with other plates, just like states share borders.

Boundaries § There are three main types of boundaries § Convergent § When plates push against each other § Divergent § When plates move away from each other § Transform § When plates slide against each other § Online animations