Layers of the Earth, Pangaea, and Movement

Planet Earth There are different layers to our planet The simplest way to break it down is into 3 layers: – Crust – Core – Mantle

How do we know about the layers? Seismic waves – Waves of energy traveling through earth Drilling – We drill down into the surface

Exploring the Layers Seismic Waves – Can pass through quickly, or bounce backward – When waves change we know the layers are different

Exploring the Layers Continued Drilling & Mining – Furthest Drill = 15km – Furthest Mine = 3.8km Future Goals – 2020 – Drill to Mantle

Composition - Crust Thin, Outer Layer – Layer we live on Generally km thick Broken into 2 different types – Oceanic – Continental

Composition - Crust Oceanic – Under Oceans – Thinner – Denser Continental – Under Continents – Thicker – Less Dense

Composition - Mantle Layer beneath the crust Thickest layer by a large amount Has a much higher pressure down there

Composition - Core Hot & Dense – 4,000-5,000°C Broken into 2 sections – Due to Physical Properties Inner Core Outer Core

Physical Properties – Outer Core Liquid Layer Creates Earth’s Magnetic Field Cooler than inner core

Physical Properties – Inner Core Solid Metal Layer Extreme Pressure

Alfred Wegener Born in 1880 PhD in Astronomy He found a paper on fossils being on either side of the Atlantic Ocean and he wanted to know more

His Theory The continents can drift apart from each other and have done so in the past – Continental Drift Evidence – Fossil – Rocks – Climate – Glaciers – Continent Shape

Scientific Process Wegener made many observations and thought that the continents were once connected – Wasn’t the first to think they were connected – Was the first to publish it and gain data Single Landmass – Pangaea “All Earth” in Greek

Disbelief Theory Not Accepted in Scientific Community – What force could move continents? – Wanted proof Some believed there were once land bridges that connected the continents but they fell apart

What Changed? Gained evidence – Studied fossils – Studied crust – Noticed slight movement

So what is happening to the oceans? ctonics/p_seafloorspreading.html ctonics/p_seafloorspreading.html

Sea-Floor Spreading Process by which new oceanic lithosphere is created as older materials are pulled away Creates Mid-Ocean Ridges – Underwater Mountain Chains

Sea-Floor Spreading Process Plates move away from each other Creates a gap in the sea floor Magma rises to fill gap Magma cools and forms underwater mountains

Newer Crust = At the Mid-ocean crust Older Crust = Edges of continents

Theory of Plate Tectonics Theory that both continental and oceanic crust move Theory states: – Top of Mantle near the surface is divided into tectonic plates that move around

Causes of Motion Heat and Gravity Convection – Hot material rises and cooler material sinks. Drags tectonic plates sideways Slab Pull – Oceanic lithosphere is denser than the asthenosphere. – Oceanic plate sinks and pulls the rest of the plate with it

Tectonic Plate Boundaries Convergent – Two plates push into another – Result depends on what type of crust Continental / continental – Push crust upward Continental / Oceanic – Oceanic plate slides under Oceanic / Oceanic – One of the plates slides under

Tectonic Plate Boundaries Divergent – Two plates move away from each other – Examples: Sea-floor spreading Mid-ocean ridges are the most common Can be found on continents

Tectonic Plate Boundaries Transform – Two plates slide past each other horizontally – Plates are smooth so they grind and jerk Cause Earthquakes – Example San Andreas Fault in California

Southern California It is right along that fault line May break away in the near future…but very slowly Moves a very small amount every year

Tracking Plate Motion Slow and Gradual Measured in centimeters per year Measure using GPS – Global Positioning System