Geology of Planets midterm

You know

\*Which is larger, Mercury or the Moon?

Mercury

\*Similarities between Mercury and the Moon:

Heavily Cratered,

Grayish surfaces

Silicates on surface

minerals like feldspars

Basalt Lavas

\*Describe the Cratered plains of mercury

Most heavily cratered part of Mercury

Less cratered than the Moon’s highlands

\*What made the smooth plains like the Lunar Maria

Flood lavas

\*Extension on Mercury

Doming and Extension in the Caloris Planitia (grabens)

Pantheon Fossae

The meteors are causing tectonic plates to move

Very straight

\*Compression/contraction on Mercury

Thrust fault and shrinkage of planet

Like the wrinkle ridges on the moon

Not very straight

\*Why is Mercury so iron-rich?

The size of the core is about 3/4 the radius

Not quite close enough to the Sun to have been vaporized by the Sun

Possible that where Mercury formed there was a lot of refractory material and more Iron condensed there

Possible that there was a bigger crust and an impact came and stripped away that crust

\*Is mars bigger than the moon and Mercury?

Yes

\*How is Mars similar to Earth?

Almost same day - 24 h and 37 m

Similar axis tilt, days and seasons are similar

\*Southern cratered highlands on Mars

Multiring basins,

high elevation

Craters highly degraded

Valley networks

Mars retained its older crust, not a ton of change

\*Mars Northern Smooth Plains

Low smooth plains

Partly volcanic

Channels from highlands empty here, water?

Partly sedimentary

Lots of water is hidden in ground ice, some of it may have gone away because there is no magnetic field

\*Crustal Domes on Mars

Not seen on Mercury or the Moon

Continent-sized tectonic features

Fractures and grabens

Came from mantle plume hitting the crust and forming a plateau/shield volcano

\*How was Tharsis formed?

Extension

\*Mars Polar Ice Caps

Because Mars has an atmosphere!

They are made of water ice and carbon dioxide ice

Ring of sand dunes

\*Impact craters on Mars

Young craters on Mars have distinctive ejecta patterns

Ejecta included a lot of water-from melted ground ice

Ejecta hit the ground and then moved like a mudflow

\*Mars Sand Dunes

Eolian system?

The sand is made from basalt and is fragmented and blown into dunes.

The arms point the wind direction

\*Martian Valley Networks

Drainages that are integrated into each other

Probably came from rainfall

Dendritic valley networks are the most ancient types of channels known

Dendritic = treelike branching

Merging into larger and larger streams downhill

Produced by precipitation or groundwater seeping at springs

Water isn’t stable as a liquid there anymore

Similar to dendritic valleys on the Earth, though Earth has better ones

\*Catastrophic floods on Mars

Come from below the surface from abundant ice/water erupting out of the ground--heated by volcanism?

Earth doesn’t have anything comparable.

It looks like a ton of impact craters or like something exploded and then ran off like water.

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\*Heat release on Mars

Large plumes rise to the surface and erupt but there are no plates to move to create volcanoes

\*Venus oddities

Very slow retrograde rotation

No magnetic field, hard to protect life on Venus

Atmosphere is 100x the Earth’s in density

\*Major provinces of Venus

Lowlands--flat

Volcanic rises or Uplands

Highlands--highly deformed

\*Venus Lowlands

Low

Broad, relatively smooth

Wrinkle ridges and fractures

Example: Atalanta Planitia

\*Volcanic rise in venus

Domes, crust is brittle,

basalt that is solidified and caused fractures

\*Highlands on Venus

Strongly deformed

15% of Venus

Compression

Extension

Examples: Ishtar Terra and Aphrodite Terra (about the size of Africa with compressional features and cut by extensional features.)

\*Other things on Venus

Shield Volcanoes

Extension--Wrinkle ridges

Mountain Belts

\*Why is Venus so hot?

Visible sunlight passes through clear atmosphere

Heats up surface

Re-radiated light at longer wavelengths than incoming (infrared)

Light absobed by clouds, water vapor, carbon dioxide and methane, reradiated again.

Heats clouds, atmosphere and surface

Greenhouse effect!

The difference between Earth and Venus is the presence of liquid water and life.

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\*Plates vs Plumes on Earth and Venus

Plumes are upwellings and those upwellings cause downwellings in other places (compression and pileup)

Earth’s plates have a cool, rigid crust that goes underneath into the mantle.

On Venus, there is no asthenosphere that the plates ride on the top of

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\*Why is Venus so hot?

Greenhouse effect

Visible sunlight passes through the atmosphere and warms the surface. The surface then re-radiates infrared energy that is absorbed by the clouds, water vapor and carbon diozide and methane are reradiated again. Which heats the surface again

This didn’t happen on Earth because of liquid water and life. They absorbed the carbon dioxide and trap it into rock

\*Impact craters on Venus

The impact adds an amount of energy that causes the rock to melt on the surface.

\*Earth’s major features

High continents (granite)

Low ocean basins (basalt)

Lots of water in the oceans and ice caps

No heavily cratered terrain

Heavy tectonic and hydrologic action

\*Earth’s atmosphere

Nitrogen because we have life to draw down the carbon dioxide.

Fossilized atmosphere--the gray rocks in the Wasatch Mountains are marine carbonates. They hold the CO2 that was once in the atmosphere.

\*Earth’s Hydrologic system

see picture

\*Earth’s Magnetosphere

Because of the Iron core, this makes it so there can be life on Earth.

\*Earth’s Tectonism

See the picture

\*Impact craters on the Earth

about 150, might be more in the ocean

Very degraded and old. The atmosphere modified it

\*Earth impact at end of mesozoic era

Ejecta found worldwide

Thickest in Caribbean

Led the search to the Yucatan peninsula of Mexico

Impactor was an asteroid 10 to 15 km across

Would you be surprised if tomorrow’s newspaper reported that a volcano was discovered erupting on Mercury?

Yes, that is not expected to happen on Mercury today.

What causes the differences between impact craters on the Moon and those on Mercury (the extent of the ejecta blanket and secondary cratering)?

Different gravitational attractions on each planet

What do thermal models of Mercury’s evolution suggest about its history?

That it developed a metallic core early in its history

The oldest types of terrains on both the Moon and Mercury are…

Heavily cratered terrain

Which of the following features are found on the Moon and Mercury? (check all that apply)

Flood lavas

Multiring basins

Impact craters

Faults related to contraction

NOT DUNES

Which of the following tectonic processes are thought to have occurred on Mercury? (Check all that apply)

Thrust faulting due to contraction of the planet

Graben formation due to extension

Mercury’s smooth plains…

May be similar in origin to the lunar maria

What explains Mercury’s iron large core? choose the two most likely

Mercury formed near the Sun in a zone that was oxygen-poor and rich in metallic iron

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A large impact stripped away the silicate shell from an already differentiated Mercury

Although both Mercury and Mars have similar gravity fields, Mars has an atmosphere whereas Mercury does not. What is a possible explanation?

Mars is more volatile rich

Which planetary body has (basically) no magnetic field today?

Mars

Which of the following are important differences between the nature of the martian hemispheres (north and south)? (mark all that apply)

(all)

Surface ages

Number of young volcanoes and volcanic plains

Elevations

The number of impact craters

How did these vast valleys on Mars form?

The outflow valleys were eroded by liquid water

Martian valley networks are…

Restricted in occurrence to the oldest parts of Mars

The outflow channels on Mars are different from river systems on Earth in what way?

They appear to come from below the surface and lack extensive collection systems

The largest dune fields on Mars are…

in the polar regions

Why does Mars lack a current, well-integrated hydrologic system?

It is too cold

What is the probable origin of the irregular ovals in this image of the surface of Mars?

Sublimation of ground ice caused collapse of the surface it make pits

What is the Tharsis bulge?

A large dome that was associated with the development of an extensive fracture system.

Mars and Mercury differ substantially in what way(s)? Choose all that apply

The compositions of their atmospheres

Their densities

The sizes of their cores

Their surface temperatures

Graben formation is usually associated with which process?

Lithospheric extension

Which features of Mars indicate a distinctive geologic process that doesn’t operate on Mercury or the Moon?

Domal upwarps of the lithosphere and associated fractures caused by mantle plumes

Which of the following statements about Venus are true? Choose all that apply

The diameter of Venus is almost the same as that of Earth.

The atmospheric gases create a large Greenhouse effect.

If Venus is so close to Earth, why has it taken so long to understand what the solid surface of Venus is like?

Its surface is buries beneath a very cloudy atmosphere.

Which of the following is a major difference between Venus and Earth?

atmospheric composition

Radar images of Venus show all of the following except…

river valleys

Which of the following statements is an accurate description of the atmosphere of Venus?

The venusian atmosphere is rich in carbon dioxide

Conditions on Venus are such that which of the following are true? Choose all that apply

Pure lead would be a liquid on its surface

The pressure is about 90 times that on Earth

What is one of the major causes of the high temperatures on the surface of Venus?

The greenhouse effect

Large amounts of water (as gas or liquid) on Venus…

have probably been lost to space and by combination with surface materials

Impact craters on Venus that are larger than about 30 km in diameter are…

not common because of the planet’s dynamic interior and young surface

About how old is the surface of Venus as judged from the impact craters?

Millions of years old

Why is the Earth a dynamic planet, whereas the Moon and Mercury have undergone very little change during the last 3.5 billion years? Select all that apply

A major difference is that Earth is much larger than the other two.

The Moon and Mercury lack atmospheres, but Earth has retained one, which has greatly modified the surface.

What are some of the ways that the advent of life modified Earth’s atmosphere/hydrosphere and the geologic processes which act on its surface? Select all that apply

Using energy from the Sun, organisms consumed carbon dioxide and released oxygen into the atmosphere

The oxygen produced by living things oxidized (weathered( the minerals and rocks at the surface

The evolution of creatures that make shells of calcium carbonate helped remove carbon dioxide from the atmosphere

Large quantities of dissolved iron were removed from the ocean to form delicately banded iron-rich sediments.

In what way is the history of Earth similar to the history of the Moon?

Both planetary bodies once had heavily cratered surfaces

What are some of the main reasons Venus and Earth have such different histories?

Any evidence of early precipitation or oceans on Venus has been erased by lava flows.

Which gas was most efficiently removed from the Earth’s atmosphere since the advent of life?

Carbon Dioxide

Which of these factors control the Earth’s hydrologic system? Mark all that apply

Gravity

Solar energy

Topography

Temperature

The presence of oxygen in a planet’s atmosphere can indicate…

The presence of living organisms

Which event drastically modified Earth’s geologic history about 3.5 billion years ago?

The advent of life

Karst topography is produced…

because limestone is relatively soluble in water

Considering the ways it forms, deforms, and crystallizes, glacial ice can be considered to be which of the following?

a metamorphic rock

On Earth and Mars, how is loess deposited? mark all that apply

As a blanket which mantles the landscape

By the wind

As dust-sized particles

A weak layer within Earth which behaves like a viscous fluid is…Mark all that apply

The outer core

The asthenosphere

How thick is Earth’s atmosphere?

Between about 10 and 200 km thick

Which of the following is not usually associated with a terrestrial subduction zone?

Basaltic shield volcanoes

The Earth’s oceanic crust is composed mostly of…

Igneous rocks of basaltic composition

Which of the following are true about mid-ocean ridges? Select all that apply

The site of the production of oceanic crust

Has abundant extensional normal faults

On Earth, lithospheric plates converge at which plate boundary?

Subduction zones

Where are the oldest rocks on Earth found?

In its continental shields

Why did continents develop on Earth and not on the Moon, Mercury, or Mars?

Only Earth has subduction zones

What do transform plates boundaries do?

offset segments of mid-ocean ridges

What are divergent plate boundaries?

The often occur in oceanic crust and produce grabens and normal faults

Oceanic crust

Oceanic crust juxtaposed to continental crust always marks a convergent plate boundary

What is the approximate age of the surface of Venus?

The average age of the surface is much younger than any of the Moon’s major terrains

Does Venus have a plate tectonic system like the Earth? Mark all that apply

No, the high surface temperature may prevent the lithosphere from becoming dense enough to subduct back into the mantle

No, Venus may lack a shallow asthenosphere

No, Venus is water-poor which makes the melting point of the mantle higher than on Earth

No, Venus is dominated by mantle plume convection instead.

Why is the history of Venus so different from that of Mars?

Venus is significantly larger than Mars and cooled slowly

What would have happened on Venus if it had been cool enough for liquid water to form?

Carbonate minerals may have formed in the water and removed the carbon dioxide from the atmosphere

T/F It is very possible that Venus once had more water and has lost it to space over the millenia

True

How many meteorite impact craters have been identified on Earth?

About 100

What explains the number of impact craters that have been identified on Earth? Select all that apply

Earth has few impact craters because its ancient surface has been extensively modified by erosional processes

Earth has few impact craters because many were obliterated by subduction, mountain building, and volcanism

How did the Chicxulub impact affect Earth?

The impact triggered a series of climate changes that led to the extinction of many species, including dinosaurs

The two large volcanoes of Venus, Theia Mons and Rhea Mons, lie on the flanks of a structure similar to which of the following?

The East African Rift valley

Folded mountain belts are important tectonic landforms. Which of the following statements is the most accurate description of folded mountain belts?

They are found around the margins of highlands on Earth and Venus

What is the most important factor in the volcanic and tectonic evolution of Venus as compared to Mars?

The size of Venus which makes it cool slower than Mars