Earth How We Know What We Know The

Earth How We Know What We Know The Outside • Rocks (free) • Maps • Many Satellites • Global Positioning The Inside • Volcanoes • Drills • Gravity • Magnetic Fields • Earthquakes

Some Earth Satellites ISS Aura ADEOS-2 ICESat-2 Earth Observing Mission 2 GOES 13 Terra

Earth

Continental Plates – Global Positioning • Surface is moving • A few cm per year

The Earth – Continental Drift

The Earth – Deep Drilling • Greatest depth drilled = 12 km

The Earth – Volcanoes • Provide samples from shallow interior of Earth

The Earth – Volcanoes

The Earth – Clues to the Interior • Gravity measures mass of Earth • Magnetic fields from interior – Fluid Layer – Conductor (metal) – Motion (rotation) • Earthquakes!

Earthquakes San Andreas Fault

Earthquakes • Different types of waves travel differently through the Earth • P-waves are pressure waves – Can travel through solids and liquids • S-waves are shear waves – Can travel through solids only • Surface waves travel only on the surface

Earth’s Interior • The Crust • Thin layer of lightweight rocks • Rigid – can’t flow • The Mantle – largest part • Denser rocks • Plastic – can be deformed slowly • Flows over time • Cores • Mostly iron • Outer core – liquid • Inner core – solid Q. 29: Earth’s Magnetic Field

Convection • Heat inside Earth causes expansion • Lower density causes hot areas to rise – Like water in a pan • Plastic mantle can flow as well • Continents carried on top of flowing mantle • Rigid crust can’t flow - it breaks instead (sometimes)

Earth’s Magnetic Field • Outer core is liquid metal • Currents can flow in it • Rotation of Earth regenerates field • Tilted compared to rotation axis • Direction/strength changes over time • Charged particles from Sun deflected by our magnetic field • Solar wind on atmosphere creates Aurora Borealis and Australis

Earth’s Magnetic Field

Factors Causing Earth’s Surface Features • Moving plates – Mountains – Ocean Trenches – Continents – Subduction • Erosion – Rain – Wind • Volcanoes

Earth – Meteor Craters Q. 30: Earth’s Meteor Craters • Atmosphere blocks or slows all but the largest meteors – Only large meteors make it through • Erosion wipes out evidence of most of these – All but the largest get eliminated over time • In the long run, volcanism and subduction eliminate the rest – The oldest craters are all gone

Barringer Meteor Crater

Bosumtwi Crater

The Earth: Atmosphere • Composition – Nitrogen – Oxygen • Moderates temperatures – Globally – Temporally

The Earth: Water • Earth is only place in Solar System with liquid water on the surface • Allows life to develop?

The Earth: Greenhouse Effect • Visible sunlight heats the surface of the Earth – Some reflected by clouds – Some reflected by Earth • Warm Earth reradiates infrared radiation – Penetrates most of atmosphere fine – Some is captured again • Since Earth is more efficient at transmitting visible than infrared, Earth is warmer than you would expect – The greenhouse effect

Greenhouse Gasses • Some gasses are better at transmitting visible than infrared – Water vapor (H 2 O) – Not very efficient, but there’s a lot of it – Carbon dioxide (CO 2) – Very efficient, reasonably abundant – Methane (CH 4) – Extremely efficient, but very little of it • Most energy production produces carbon dioxide – Coal – produces the most – Oil – produces a lot – Natural gas – produces some – Nuclear, Solar, wind, Geothermal, etc. – produces none

Life on Earth • Earth contains oxygen because of plants • Plants also absorb carbon dioxide • Killing plants warms the Earth Q. 31: Life on Other Planets