Transcript Planet Earth

Planet Earth
Earth’s Formation
• The earth formed by
accretion of dust and small
objects in the early solar
system.
orbital
motion
– Heat from collisions
– Melt and reform
collision
• Earth rocks are compared
to meteorites and moon
rocks.
different
orbit
Layers in the Earth
• Heating the earth caused the heavy metals to sink and
lighter minerals to rise.
inner core
outer
core
mantle
crust
Seismic Waves
• Earthquakes near the
surface create vibrations.
– P waves compress
– S waves shake, slower
• Waves can be measured at
surface points far away.
– Interior information
Core
• The earth’s core consists of
iron and other metals.
– 3500 km radius
• Radioactivity keeps it hot.
– Temperature to 6500 K
– Liquid metal outer core
• Density keeps part solid.
– Solid within 1200 km
– Pressure over 1 million
atmospheres
U Colorado
Mantle
• Lighter minerals congregated above the core.
– Silicates: silicon, aluminum, magnesium, oxygen
– Iron, too
• The mantle is solid, but plastic.
– Slow movement, like putty under pressure.
crust
mantle
outer core
convection
Crust
• The crust is the cool, hard surface of the mantle.
– ocean - more dense, basalt rock
– continents - less dense, granite rock
• The crust is very thin; 10 km out of 6400 km radius.
ocean floor
crust
mantle
outer core
continent
Plate Tectonics
• Motion in the mantle causes the
crust to split.
– Earthquakes, mountains, volcanoes
• Plate tectonics causes continents to
move over millions of years.
overriding plate
crust
mantle
descending plate
outer core
ZME Science
Hot Plumes
• The heat from the outer core causes molten rock to rise
through the mantle.
– Surface rises
• The dense rock causes gravity to be very slightly higher.
bulge at the surface
crust
mantle
outer core
plume
Volcanism
• Plumes that push material to the surface form volcanoes.
• Gases and minerals in volcanoes tell us about the earth’s
mantle.
volcano
crust
mantle
outer core
plume