Mercury- craters, smooth plains and cliffs. Closest planet
to the sun.
Venus- volcanoes and few craters.
Moon- craters and smooth plains.
Earth is the only planet to have water on its surface.
Earth:
Core:
highest density; nickel and iron
Mantle:
moderate density; silicon and oxygen
Crust:
lowest density; granite and basalt
Gravity pulls high-density material to center.
Lower-density material rises to surface.
Material ends up separated by density.
A planets’ outer layer of cool, rigid rock is call the
lithosphere.
It floats on the warmer softer rock that lies beneath.
Rock stretches when pulled slowly but breaks when
pulled rapidly.
The gravity of a large world pulls slowly on its rocky
content, shaping the world into a sphere.
Heat drives geological activity:
Convection:
hot rock rises, cool rock falls.
One convection
cycle takes 100 million years on earth.
Sources of internal heat
Gravitational
potential energy of accreting planetesimals.
Differentiation
Radioactivity
Cooling of interior
Convection:
transports heat as hot material rises and cool material
Conduction:
transfers heat from hot material to cool material.
Radiation: sends
energy into space.
Role of size
Smaller
worlds cool off faster and harden earlier.
The moon
and mercury are now geologically “dead”.
Surface area-to-volume ratio
Heat content
depends on volume.
Loss of
heat through radiation depends on surface area.
Time to
cool depends on surface area divided by volume.
Larger
objects have a smaller ratio and cool more slowly.
Impact cratering
Impacts
by asteroids or comets
Volcanism
Eruption
of molten rock onto surface
Tectonics
Disruption
of a planet’s surface by internal stresses.
Erosion
Surface
changes made by wind water, or ice.
1 comment:
Very efficient, Chris!
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