GEOL 1301- Intro to Earth

(Layers, Systems, and Plate Tectonics)

Density

• intrinsic property of an object 

• measure of the mass of an object per unit of volume

• does not depend on the size or shape of the object

• affected by the of an object

• object with a higher mass or a smaller volume will have a higher density

Inner Core

• solid

• composed of iron-nickel alloy

Outer Core

• liquid

• movement of iron in this layers creates Earth’s magnetic field

7

Inner Core

6

Outer Core

2 (yellow)

Lower Mantle

2 (orange) 

Asthenosphere

5

Upper Mantle

Lower Mantle

• solid, strong

Asthenosphere 

• soft and weak but still solid

• partially molten

• temperature and pressure conditions causes melting of rocks= production of magma

Upper Mantle

• solid

• together w/ the crust is called the lithosphere

Continental Crust

• thick (25-40 mi)

• made up of less dense elements (Si, O, Al, K → granite)

Oceanic Crust

• thin (5 mi)

• contains denser elements (Fe, Mg → basalt)

Divergent Boundaries

• also known as Constructive Boundaries

• most are mid-ocean ridges, but some happen on continents

• adds new crust to Earth

• ex. Iceland, East Africa

• shallow earthquakes near their focus points

• ← →

Convergent Boundaries

• also known as Destructive Boundaries

• collision between plates

• destroys old crust

• largest earthquakes

• → ←

Oceanic-oceanic Convergence

• Magma forms and creates chains of underwater volcano islands, as well as deep ocean trenches

• ex. Japan, Indonesia

Continent-oceanic Convergence

• Oceanic plate is subducted beneath continent because it’s more dense and the continental crust is more buoyant (can float over water)

• deep ocean trenches are still present, but instead volcanic mountains are produced

• ex. Andes Mts., Cascade Mts.

Subduction

• process where one plate is forced beneath another

• oldest and densest plate sinks and subducts beneath the other plate

• continental crust= granite, thicker

• oceanic crust= basalt, thinner

Continent-continent Convergence

• no subduction but there is some initial subduction 

• no volcanoes, instead high mountains are formed

• ex. Himalayas, Alps

Transform Boundary

• also known as a Connecting Boundary

• Common in ocean where they link offsetting divergent boundaries

• large earthquakes up to M8

• ex. San Andreas Fault, Dead Sea, Alpine Fault

• Forces within tectonic plates cause stress for horizontal movement