Chapter 9

Planetary Geology


Impact Craters vs Geologic Action (You Tube)

Introduction to the Terrestrial "Worlds": Mercury, Venus, Earth, Earth's Moon, & Mars

Mercury, Venus, Earth

Moon, Mars

Size comparison

When put in order from small to large (Moon, Mercury, Mars, Venus and Earth), see trends

Consider Craters and Volcanoes/Volcanic Plains


Moon and Mercury on same scale

Surface of our Moon

Surface of Mercury

Global Surveyor Map of Mars

Craters on Mars

Venus (also Earth)

Magellan Map of Venus

craters on Venus


Crater Lake, Oregon on Earth

Crater Lake, topographical map

Smaller worlds have more craters/area and most are old, larger worlds have few craters and all were relatively recent

Volcanoes and Volcanic Plains:

Ravioli vs the Volcano (You Tube, looped)

the Moon's maria

old lava in Mercury crater (left image)

Olympus Mons Volcano on Mars (acute view)

Olympus Mons Volcano on Mars

Olympus Mons vs Earth's mountains

Idunn Mons volcano on Venus(APOD)

Mount Etna on Earth (APOD)

Volcanos on Earth

Chilean volcano (1993)

Smaller worlds have had less volcanic activity and it was long ago, larger worlds have had lots of volcanic activity and some of it was very recent

How to Make Craters

Cratering by Impacts

Rebound in center of right figure = Tycho crater on the Moon

Rate of making craters

Estimating the Age of a Surface

How to Make Volcanoes and Volcanic Plains


Making a mare

Thick vs Thin Lava -> flat vs steep Volcanos


Tharsis Bulge, topographic map of Mars (APOD)

scale of Mars topography

Corona on Venus

Magellan Map of Venus (again)

Venus coronas 30 degree view (APOD)

Explanation for coronae

Stone Mountain "pluton" in Georgia (Google maps)

Consider Signs of Tectonic Behavior on the Various Terrestrial Worlds

Movement of Earth's plates (You Tube, looped)

Wrinkled mare on the Moon

Fault line on the Moon

Signs of Shrinkage on Mercury

Valles Marineris on Mars (another image)

Magellan Map of Venus (again)

elevation map of Venus shows continents

Aphrodite Terra continent on Venus

Ishtar Terra continent on Venus

Valles Marineris on Mars

Scale of Valles Marineris

Map of Earth's Tectonic Plates

another Map of Earth's Tectonic Plates

Movement of Plates over 200 Million Years

South America and Africa fit together

Smaller worlds have had some tectonics, but larger worlds have had more and the Earth is very active, even now

How/Why the crust moves

Two Types of Crust

Motion, side view (Mid-Atlantic Ridge, South America, Africa )

Motion, side view (North America, Atlantic Ocean, Europe)

Subduction, side view

Compacted regions and stretched regions

Colliding continental crust -> pushes up mountains


Red Sea Rift Valley

San Andreas Fault

Inside the Terrestrial Planets

Simulated Convection (You Tube, looped)

Inside the Terrestrial Planets

Diagram of Mantle, Crust, Lithosphere

Waves inside Earth

S and P Waves

Stretch vs Break

Magnetic Field

The Reason Why Larger Planets Remain Geologically Active for Longer Times

Larger planets have retained more heat:

Essentially they have smaller ratios of (heat loss)/(thermal energy)

because they have smaller ratios of surface area / volume

Heating the Inside of a Planet

Cooling a Planet

Water, Wind, Erosion

Animation of Curiosity Rover on Mars (You Tube)


building atmosphere on Earth

water on Moon (newspaper October 27, 2020)

Mercury's craters (and shadowed ice)

Mars ice caps

hemitite "Blueberries" formed in water on Earth and Mars

Dry Riverbed on Mars

Erosion Channels on Mars

Gullies on Mars

Other Signs of Past Water on Mars

Sedimentary layers (Mars)

More sedimentary layers (Mars)

Substantial atmosphere on Venus

Example: Water Erosion on Earth

compare with Earth's Grand Canyon

New River (view from Va)

water causing erosion

making sedimentary layers

Four types of erosion-related surface modifications on Earth (river erosion, glacers, wind, sediment build up)

Tiny Impacts turn surface of Moon to Dust

Footprints in the regolith

Dust on the Moon

Additional Images: A Closer Look at the Moon, Mercury, and Mars

Mercury's craters (middle = Calaris Basin)

Mercury's core (compared with Earth's)

Mars's Interior

Olympus Mons Volcano on Mars (acute view)

Olympus Mons Volcano on Mars (top view)

Additional Images: Venus and the Earth

Volcano on Venus

Picture of Venus, without Atmosphere


Two Types of Crust (again)

Hot spots

Grand Canyon (again)

Additional Images: The Surfaces of Terrestrial Planets and Why They Look Like What They Do

Cratering by Impacts (again)

Examples (Arizona, Tycho on Moon)

Craters with unusual features

Eruptions and Outgassing

Effects of Size, Distance, Rotation

Additional Images: The Moon and Mercury

Moon and Mercury on same scale (again)

The Moon's maria (again)

Making a mare (again)

Additional Images: Geology of Mars

Canals on Mars (not really)

Global Surveyor Map of Mars (again)

Flyover of Mars (movie) from Mars Orbiter Laser Altimeter

Dry Riverbed on Mars (again)

Erosion Channels on Mars (again)


extra image

Gullies on Mars

Additional Images: Geology of Venus

Picture of Venus, without Atmosphere

Venera View of Surface of Venus

Lava Domes on Venus

Additional Images: Geology of Earth

Crater Lake, Oregon (movie)

Earth's Tectonic Plates (again)

Two Types of Crust (again)

Cause of Plate Tectonics (again)

North America


Hawaiian Islands