© sierra college astronomy department 1 geology of the terrestrial planets terrestrial

© Sierra College Astronomy Departmen© Sierra College Astronomy Departmentt

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Geology of the Terrestrial Geology of the Terrestrial PlanetsPlanets

Terrestrial

Midterm!Midterm!Part I Part I (Take home exam, including 10 points (Take home exam, including 10 points from Mastering Astronomy, from Mastering Astronomy, 50 pts50 pts)) isis available, due October 26available, due October 26thth, noon, noonThis week, This week, Part IIPart II ( (in class examin class exam, , 50 pts50 pts.).)– Taken in 3Taken in 3rdrd hour hour (week of 10/22 to 10/25) (week of 10/22 to 10/25)– Bring SCANTRON (882 form) and #2 pencilBring SCANTRON (882 form) and #2 pencil– Based on “Review Questions” handout, available Based on “Review Questions” handout, available

now!now!

Also: 10 of the 25 extra credit points are due Also: 10 of the 25 extra credit points are due by October 26by October 26thth, noon., noon.


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Lecture 9: Terrestrial Geology BasicsLecture 9: Terrestrial Geology Basics

The Moon and MercuryThe Moon and Mercury

The Moon’s geologyThe Moon’s geologyThe Moon’s surface can be divided into The Moon’s surface can be divided into two main landforms: two main landforms: lunar marialunar maria and and highlandshighlands (mountainous and cratered) (mountainous and cratered) regions.regions.MariaMaria (plural of (plural of maremare) are any of the ) are any of the lowlands of the Moon (some circled by lowlands of the Moon (some circled by mountains) that resemble a sea when mountains) that resemble a sea when viewed from Earth.viewed from Earth.

Moon

MoonMercury

Moonfeatures

Nearly Full Moon

The Far side of the Moon


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The Moon’s SurfaceThe Moon’s SurfaceThe The MariaMaria were caused (3 to 4 billion years ago, just after the were caused (3 to 4 billion years ago, just after the Moon was formed) by large impacts cracking through the crust Moon was formed) by large impacts cracking through the crust and the consequent magma flow from the Moon’s mantle.and the consequent magma flow from the Moon’s mantle.Asymmetry of maria between the two sides of Moon is caused Asymmetry of maria between the two sides of Moon is caused by differences in crust thickness (which ranges in depth from by differences in crust thickness (which ranges in depth from 60-100 km and is thinner on Earth-facing side).60-100 km and is thinner on Earth-facing side).This asymmetry also lead to the “locking” of one face of the This asymmetry also lead to the “locking” of one face of the Moon always towards the Earth (since the maria are made of Moon always towards the Earth (since the maria are made of denser materials).denser materials).The interior of the Moon has cooled too much for this to occur The interior of the Moon has cooled too much for this to occur againagainMicrometeoritesMicrometeorites, sand sized particles from space, remain as , sand sized particles from space, remain as the only major erosion processthe only major erosion process

interior

Moon Mareforms


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Walking on the Moon

Apollo 17December 1972surface


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The Moon and MercuryThe Moon and MercuryMercury’s geology – extreme conditionsMercury’s geology – extreme conditions

Radar observations show that Mercury rotates once Radar observations show that Mercury rotates once very 58.65 Earth days, which is precisely 2/3 of its very 58.65 Earth days, which is precisely 2/3 of its orbital period.orbital period.Mercury’s solar day is quite different from its sidereal Mercury’s solar day is quite different from its sidereal day. The solar day is 176 Earth days long (two day. The solar day is 176 Earth days long (two Mercurian years.)Mercurian years.)Only 2 longitudes on Mercury experience noon while Only 2 longitudes on Mercury experience noon while the planet is at perihelionthe planet is at perihelionHigh temperatures on Mercury can reach 425°C High temperatures on Mercury can reach 425°C (790°F), well above the melting point of lead (330°C (790°F), well above the melting point of lead (330°C or 626°F).or 626°F).On the night-side of Mercury, temperatures can fall to On the night-side of Mercury, temperatures can fall to -150°C (-250°F).-150°C (-250°F).

MoonMercury


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Mercury and the MoonMercury and the Moon

Mercury’s geology Mercury’s geology - - Moon ComparisonMoon Comparison

Mariner 10Mariner 10 flew by Mercury in 1974 (and flew by Mercury in 1974 (and subsequently twice more), returning a total of 4,000 subsequently twice more), returning a total of 4,000 photographs for the three fly-bys.photographs for the three fly-bys.Mercury appears similar to our Moon; both are Mercury appears similar to our Moon; both are covered with many impact craters.covered with many impact craters.Mercury’s craters are less prominent; the planet’s Mercury’s craters are less prominent; the planet’s surface gravity is twice that of the Moon so loose surface gravity is twice that of the Moon so loose material will not stack as steeply.material will not stack as steeply.Ray patterns are also less extensive on Mercury Ray patterns are also less extensive on Mercury because of the higher gravity.because of the higher gravity.

S1

MosaicMap


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Mercury’s SurfaceMercury’s Surface

Mercury’s surface history is thought be:Mercury’s surface history is thought be:– Mercury was hot and melted due to radioactive Mercury was hot and melted due to radioactive

decay and expanded in sizedecay and expanded in size– This fractured the crust and allowed lava to reach This fractured the crust and allowed lava to reach

the surface to form the the surface to form the intercrater plainsintercrater plains– Lava eruptions in impact basins formed theLava eruptions in impact basins formed the

smooth plainssmooth plains– Then the interior cooled and the planet shrunk Then the interior cooled and the planet shrunk

cracking the surface forming thecracking the surface forming the scarpsscarps– This probably happened in the first 700 million This probably happened in the first 700 million

years after Mercury formedyears after Mercury formed

Intercraterplain

Smoothplains

scarps

S2Scarp

6_a2MercScarp

ShrinkMerc

MercuryComposite by

Mark Robinson (Northwestern)

From Sky &

Telescope (September

2004)

NewMerc


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Mercury and the MoonMercury and the Moon

A large “bulls-eye” impact crater called A large “bulls-eye” impact crater called Caloris Basin is visible.Caloris Basin is visible.

The Moon has a similar impact regionThe Moon has a similar impact region

This impact was so intense that there is This impact was so intense that there is broken terrain in the region opposite of broken terrain in the region opposite of the Caloris basinthe Caloris basin

Calorisschematic

S3Caloris

S4-Moon

CalorisBasin


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Lecture 9: The Terrestrial PlanetsLecture 9: The Terrestrial Planets

MarsMarsHistorical MarsHistorical Mars

William and Caroline Herschel made first extensive William and Caroline Herschel made first extensive observations of Marsobservations of Mars– In 1784, W. Herschel spoke with confidence about “inhabitants” of MarsIn 1784, W. Herschel spoke with confidence about “inhabitants” of Mars

In 1879 Schiaparelli’s drawing of channels or In 1879 Schiaparelli’s drawing of channels or canalicanali on Mars on Mars was misinterpreted by the public to mean canals dug by a race was misinterpreted by the public to mean canals dug by a race of intelligent beings.of intelligent beings.– Schiaparelli may have had an eye defect which made some details appear Schiaparelli may have had an eye defect which made some details appear

as channelsas channels

Lowell, who opened his observatory in Flagstaff, AZ, in 1894, Lowell, who opened his observatory in Flagstaff, AZ, in 1894, reported he saw many canals. Other astronomers could not reported he saw many canals. Other astronomers could not confirm his findings.confirm his findings.

Changes in the dark areas on Mars led to speculation that Changes in the dark areas on Mars led to speculation that there is vegetation on the planet that changes color in there is vegetation on the planet that changes color in response to seasonal growth.response to seasonal growth.

Mars by Lowell

Lowell v Photo

Mars’s Canals?


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MarsMars

Mars’s BasicsMars’s BasicsMars orbits the Sun at an average of 1.524 AU Mars orbits the Sun at an average of 1.524 AU (about 228 million km).(about 228 million km).Mars’ orbit is more eccentric than Earth’s, so Mars’ orbit is more eccentric than Earth’s, so Mars’ distance from the Sun varies from 210 Mars’ distance from the Sun varies from 210 million km to 250 million km.million km to 250 million km.Mars takes 1.88 Earth years to complete its Mars takes 1.88 Earth years to complete its orbit around the Sun.orbit around the Sun.Polar caps of water-ice and carbon dioxide can Polar caps of water-ice and carbon dioxide can be seenbe seen


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MarsMars

Mars’ sidereal period is 24Mars’ sidereal period is 24hh3737mm; its ; its solarsolar day is 24day is 24hh4040mm long, very similar to that of long, very similar to that of Earth.Earth.

Mars’ equator is tilted 25.2° with respect to Mars’ equator is tilted 25.2° with respect to its orbital plane, close to Earth’s 23.4°.its orbital plane, close to Earth’s 23.4°.

We see seasons on Mars as we do on We see seasons on Mars as we do on Earth.Earth.– The polar caps grow and shrink accordinglyThe polar caps grow and shrink accordingly

Mars Rotation

Mars Seasons


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Mars as Seen from EarthMars as Seen from Earth

Mars is best seen at Mars is best seen at oppositionopposition, once every every 2.2 , once every every 2.2 years (= 780 days = synodic period)years (= 780 days = synodic period)– All oppositions are not equal due to the significantly elliptical orbit All oppositions are not equal due to the significantly elliptical orbit

of Mars, so every 15 to 17 years Mars has a much closer than of Mars, so every 15 to 17 years Mars has a much closer than average oppositionaverage opposition

Other special points on Mars’s (or any other outer planet’s) Other special points on Mars’s (or any other outer planet’s) orbit: orbit: – ConjunctionConjunction, , eastern and western quadrature, eastern and western quadrature, oppositionopposition

Mars can exhibit a significant gibbous phase near Mars can exhibit a significant gibbous phase near quadraturequadrature

Lecture 9: The Terrestrial PlanetsLecture 9: The Terrestrial Planets

MarsMars

S1

Mars at Quadrature

Configs

PA

A

P

Oppositions of Mars (1997 – 2010)

2003

2001

2010

2007 2005

1997

1999

0.37

0.56 0.46

0.66

0.66

0.58 0.45

Mars during its opposition in 2003MarsObs


2020

Geology of MarsGeology of MarsBesides the polar caps, Mars has other Besides the polar caps, Mars has other remarkable featuresremarkable featuresThe southern hemisphere has most of the The southern hemisphere has most of the higher elevation and the great impact region higher elevation and the great impact region called Hellas Basin and most of the impact called Hellas Basin and most of the impact craterscratersThe northern hemisphere has the lower The northern hemisphere has the lower elevation, few impact craters and most of the elevation, few impact craters and most of the volcanoesvolcanoes


MarsMars

Altitude Maps of Mars from the Mars Global Surveyor (MGS)


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MarsMars

The largest volcano is Olympus Mons, who The largest volcano is Olympus Mons, who height of 24 km (15 mi) is twice that of Earth’s height of 24 km (15 mi) is twice that of Earth’s largest mountain.largest mountain.– Several other large volcanoes can be found in the Several other large volcanoes can be found in the

surrounding surrounding Tharsis RegionTharsis Region

One reason Mars can “grow” larger volcanoes One reason Mars can “grow” larger volcanoes than Earth is because they lack Earth-like than Earth is because they lack Earth-like tectonic plates. Formed over a hot spot of lava tectonic plates. Formed over a hot spot of lava that wells up from within a planet, a volcano that wells up from within a planet, a volcano can grow to enormous size if it does not move can grow to enormous size if it does not move off the hot spot.off the hot spot.

S3,4

OlympusMons


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MarsMarsThere were some tectonic activities in Mars’ past: There were some tectonic activities in Mars’ past: Valles Valles MarinerisMarineris is an enormous canyon on Mars that stretches is an enormous canyon on Mars that stretches nearly 4,800 km (3,000 mi).nearly 4,800 km (3,000 mi).– However, it was not carved out by a river nor a result of Earth-like plate However, it was not carved out by a river nor a result of Earth-like plate

tectonicstectonics– Instead it is a split in the crust which caused the Tharsis Region to Instead it is a split in the crust which caused the Tharsis Region to

bulge outwardbulge outward– There do appear to be runoff channels on the edges of the canyon There do appear to be runoff channels on the edges of the canyon

which may have been formed by the outpouring of subsurface waterwhich may have been formed by the outpouring of subsurface water

There may be current geologic actively, though Mars will “die” There may be current geologic actively, though Mars will “die” in the next few billion yearsin the next few billion years

S5

S9,10

Valles Marineris


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Ancient Water on MarsAncient Water on MarsCould Mars have been water filled in its past?Could Mars have been water filled in its past?– Outflow channels seem to imply that water flowed 2-3 Outflow channels seem to imply that water flowed 2-3

billion years ago (based on crater counts)billion years ago (based on crater counts)

RoversRovers Spirit Spirit and and OpportunityOpportunity (Mars Exploration (Mars Exploration Missions: Missions: MER-MER-AA and MER- and MER-B; B; RoversRovers) landed on Mars ) landed on Mars in 2004 looking for evidence of ancient waterin 2004 looking for evidence of ancient water– OpportunityOpportunity found rocks that must have been soaking in found rocks that must have been soaking in

water at some time: Jarosite and the “blueberries” water at some time: Jarosite and the “blueberries” containing hematitecontaining hematite


MarsMars blueberries

blueberries2

Outflowchannels

http://marsrovers.jpl.nasa.gov/home/


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MarsMars

Present Water on MarsPresent Water on MarsUnder the current conditions, free flowing water Under the current conditions, free flowing water is unlikely to exist on Mars since the pressure is unlikely to exist on Mars since the pressure and temperature are too low.and temperature are too low.– Water will only exist as a gas or solid on MarsWater will only exist as a gas or solid on Mars– However, there is evidence of “gullies” which seemed However, there is evidence of “gullies” which seemed

to have running water in the recent pastto have running water in the recent past

However, water or water-ice may exist just However, water or water-ice may exist just underneath the surface of the planet.underneath the surface of the planet.– OdysseyOdyssey and and Mars ExpressMars Express orbiter both saw evidence orbiter both saw evidence

for subsurface waterfor subsurface water

Odyssey subH20

Channels1.5km

Midterm!Midterm!Part I Part I (Take home exam, including 10 points (Take home exam, including 10 points from Mastering Astronomy, from Mastering Astronomy, 50 pts50 pts)) isis available, due October 26available, due October 26thth, noon, noonThis week, This week, Part IIPart II ( (in class examin class exam, , 50 pts50 pts.).)– Taken in 3Taken in 3rdrd hour hour (week of 10/22 to 10/25) (week of 10/22 to 10/25)– Bring SCANTRON (882 form) and #2 pencilBring SCANTRON (882 form) and #2 pencil– Based on “Review Questions” handout, available Based on “Review Questions” handout, available

now!now!

Also: 10 of the 25 extra credit points are due Also: 10 of the 25 extra credit points are due by October 26by October 26thth, noon., noon.


2828

Currently there:Currently there:– Mars Global SurveyorMars Global Surveyor andand OdysseyOdyssey

(Orbiters;Relays)(Orbiters;Relays)– SpiritSpirit and and OpportunityOpportunity (Mars Exploration Missions: (Mars Exploration Missions:

MER-MER-AA and MER- and MER-B; B; RoversRovers))– Mars ExpressMars Express

Beagle 2Beagle 2 roverrover crashed on surface, but crashed on surface, but orbiterorbiter is is working fine and it is taking some of the highest working fine and it is taking some of the highest resolution pictures of the Martian surface ever from orbitresolution pictures of the Martian surface ever from orbit

– Mars Reconnaissance OrbiterMars Reconnaissance Orbiter (Launched: 12 Aug (Launched: 12 Aug 2005)2005)

Even higher resolution of surface, subsurface, Even higher resolution of surface, subsurface, atmosphere (Inserted in Martian orbit on 10 March atmosphere (Inserted in Martian orbit on 10 March 2006, aerobraking has put into proper low orbit)2006, aerobraking has put into proper low orbit)


Current and Upcoming Mars MissionsCurrent and Upcoming Mars Missions

MRO

http://marsrovers.jpl.nasa.gov/home/

http://www.esa.int/SPECIALS/Mars_Express/

http://www.nasa.gov/mission_pages/MRO/main/index.html

http://www.nasa.gov/mission_pages/MRO/main/index.html


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Up next:Up next:– Phoenix Phoenix landerlander (2007)(2007)

Digger arms, oven and portable laboratoryDigger arms, oven and portable laboratory

– Mars Science Laboratory (2009)Mars Science Laboratory (2009)Bigger and better roverBigger and better rover


Current and Upcoming Mars MissionsCurrent and Upcoming Mars Missions

http://phoenix.lpl.arizona.edu/mission.php




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Venus’s MotionsVenus’s Motions

Venus is easily seen in the sky with a maximum Venus is easily seen in the sky with a maximum elongation of 47 degreeselongation of 47 degrees– (Ancient Greek names: Hesperus (evening) and (Ancient Greek names: Hesperus (evening) and

Phosphorus (morning))Phosphorus (morning))

Special points on Venus’s (or Mercury’s orbit):Special points on Venus’s (or Mercury’s orbit):– Inferior and superior conjunctionInferior and superior conjunction

– Greatest western (morning) and eastern (evening) Greatest western (morning) and eastern (evening) elongation Each of these is repeated every 584 days elongation Each of these is repeated every 584 days (Synodic period)(Synodic period)


VenusVenus

Orbitdiagram

Venus at Crescent


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Venus’s MotionsVenus’s Motions

Venus can be seen high in the sky around maximum Venus can be seen high in the sky around maximum elongation setting up to 3-4 hours after sunset (or rising 3-elongation setting up to 3-4 hours after sunset (or rising 3-4 hours before sunrise)4 hours before sunrise)

Venus can sparkle so brilliantly that it is often mistaken for Venus can sparkle so brilliantly that it is often mistaken for an airplane (or UFO) and in a dark site can even cast a an airplane (or UFO) and in a dark site can even cast a shadow (!)shadow (!)

Venus can be seen in the daytime under clear sky Venus can be seen in the daytime under clear sky conditions, if you know where to lookconditions, if you know where to look

Like Mercury, Venus can transit the Sun, but is far rarerLike Mercury, Venus can transit the Sun, but is far rarer

Lecture 8a: The Terrestrial PlanetsLecture 8a: The Terrestrial Planets

VenusVenusStarry


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What are the Major Geological Features of Venus?What are the Major Geological Features of Venus?

Since Venus is only 5% smaller than the Earth, we expect it to Since Venus is only 5% smaller than the Earth, we expect it to be geologically activebe geologically active

Orbiting probes Orbiting probes Pioneer Venus 1Pioneer Venus 1 (1978), (1978), Venera 15 Venera 15 andand 16 16 (1983-84), and (1983-84), and MagellanMagellan (1990-93) have produced detailed (1990-93) have produced detailed radar maps of Venus’s surface.radar maps of Venus’s surface.

About two-thirds of Venus’s surface is covered with rolling hills. About two-thirds of Venus’s surface is covered with rolling hills. Highlands occupy <10% of the surface, with lower-lying areas Highlands occupy <10% of the surface, with lower-lying areas making up the rest.making up the rest.

Venus has about 1,000 craters that are larger than a few Venus has about 1,000 craters that are larger than a few kilometers in diameterkilometers in diameter


VenusVenusVenus

S5-S9Skip?

Venus RadarGlobe

Venus RadarMap

Venus as seen in the UV

Pictures taken 5 hours apartClouds take about 4-5 days to circle planet


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What are the Major Geological Features of Venus?What are the Major Geological Features of Venus?

While it has volcanoes and a lithosphere contorted by While it has volcanoes and a lithosphere contorted by tectonics, Venus has some unique features, such as tectonics, Venus has some unique features, such as coronaecoronae, probably made of hot rising plumes of mantle , probably made of hot rising plumes of mantle rock.rock.

Volcanoes are still active (erupting in the last 100 million Volcanoes are still active (erupting in the last 100 million years) since the atmosphere contains sulfuric acidyears) since the atmosphere contains sulfuric acid

There is the lack of erosion on Venus: the winds are There is the lack of erosion on Venus: the winds are very weak.very weak.


VenusVenus

Venussurface

Venusianfeatures


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What are the Major Geological Features of Venus?What are the Major Geological Features of Venus?Venus has a lack of Earth-like plate tectonics: no super high mountain Venus has a lack of Earth-like plate tectonics: no super high mountain rangesranges

Crater counts are uniform across the planet, suggesting an uniform Crater counts are uniform across the planet, suggesting an uniform age for the planet’s surface which is estimated to be 750 million years age for the planet’s surface which is estimated to be 750 million years old. The uniformity of this age suggest that the entire planet “repaved” old. The uniformity of this age suggest that the entire planet “repaved” itself at that time.itself at that time.

Since Venus should be a warm underneath the lithosphere as the Since Venus should be a warm underneath the lithosphere as the Earth, the lithosphere of Venus must be thicker than that of the Earth Earth, the lithosphere of Venus must be thicker than that of the Earth and resists fracturing into piecesand resists fracturing into pieces– No direct proof of thisNo direct proof of this

– May have come about from higher temperature surfaceMay have come about from higher temperature surface


VenusVenus


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The Earth is the most active of the The Earth is the most active of the terrestrial worldsterrestrial worlds– The Earth’s size explains the abundance of The Earth’s size explains the abundance of

internal heatinternal heat– The erosion from wind and water is The erosion from wind and water is

explained by the Earth’s distance from the explained by the Earth’s distance from the Sun and the rotation rateSun and the rotation rate

– The Earth’s plate tectonics is unique among The Earth’s plate tectonics is unique among the terrestrial worlds.the terrestrial worlds.


The Unique Geology of Earth


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Plate tectonics is the movement of Plate tectonics is the movement of fractured pieces of the lithosphere or fractured pieces of the lithosphere or plates.plates.

The plates of the Earth “float” on the The plates of the Earth “float” on the mantle as convection moves the plate mantle as convection moves the plate about the surface.about the surface.

The plates move at a rate of a few The plates move at a rate of a few centimeters per year – about the rate of centimeters per year – about the rate of fingernails on a human handfingernails on a human hand


The Earth’s surface in motion

Drift

Plates


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Plate TectonicsPlate Tectonics

Continental MotionContinental MotionAlfred Wegener is credited with first Alfred Wegener is credited with first developing the idea of developing the idea of continental driftcontinental drift - - the gradual motion of the continents relative the gradual motion of the continents relative to one another.to one another.He noticed that the coasts of South America He noticed that the coasts of South America and Africa seem to fit together and that the and Africa seem to fit together and that the continents shared similar fossilscontinents shared similar fossilsNot initially accepted because a mechanism Not initially accepted because a mechanism to move continents was not known.to move continents was not known.

Drift

Plates2

SAAfr


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Plate TectonicsPlate TectonicsIn the mid-1950s began to observe In the mid-1950s began to observe evidence for continental motion: mid-evidence for continental motion: mid-ocean ridgesocean ridges

Mantle material erupts onto the Mantle material erupts onto the ocean floor, pushing apart the ocean floor, pushing apart the existing seafloor on the either side. existing seafloor on the either side. This is referred to as This is referred to as seafloor seafloor spreadingspreading

RiftSubduc

Drift

tectonics

Plates2


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The Earth’s surface has two very different types The Earth’s surface has two very different types of crust: of crust: seafloorseafloor and and continentalcontinental– The The seafloor crustseafloor crust is thinner, denser, and younger is thinner, denser, and younger

It’s typically 5-10 km thinkIt’s typically 5-10 km thinkThese plates get renewed in a process called These plates get renewed in a process called subduction subduction and so the seafloor crustand so the seafloor crust is never more the 200 million years is never more the 200 million years old.old.As a result, the continents have been spreading away from As a result, the continents have been spreading away from each other for 200 million years.each other for 200 million years.

– The continental crust is thicker, less dense, and olderThe continental crust is thicker, less dense, and olderTypically between 20 and 70 km in thickness though its Typically between 20 and 70 km in thickness though its weight pushes it down so that it only sticks out slight higher weight pushes it down so that it only sticks out slight higher than the seafloor.than the seafloor.Can be as old as 4 billion years.Can be as old as 4 billion years.


Plate TectonicsPlate TectonicsPlates2

subduction

2 crusts


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Building up continents Building up continents Unlike seafloor crust, which get recycled, continental Unlike seafloor crust, which get recycled, continental crusts are gradually growing with timecrusts are gradually growing with timeVolcanism shapes west North America as volcanic Volcanism shapes west North America as volcanic islands have merged into the rest of North Americaislands have merged into the rest of North AmericaErosion played a big role the Great Plains and MidwestErosion played a big role the Great Plains and MidwestSome mountains were formed when one plate Some mountains were formed when one plate subducted under anothersubducted under anotherWhen two continent-bearing plates collided with each When two continent-bearing plates collided with each other they also produced mountains. The Appalachians other they also produced mountains. The Appalachians formed from several collisions: two from South America formed from several collisions: two from South America and one from western Africa.and one from western Africa.


Plate TectonicsPlate Tectonics Plates2subduction

Major geol.features

Himalayas


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Rifts, Faults, and Earthquakes Rifts, Faults, and Earthquakes When continental plate are pulling apart, we When continental plate are pulling apart, we can get a can get a rift valley rift valley like the one in East Africalike the one in East Africa

Plates that slide sideways are called Plates that slide sideways are called faultsfaults– San Andreas is famous example and will eventually San Andreas is famous example and will eventually

bring LA and SF together in 20 million yearsbring LA and SF together in 20 million years– When a fault moves it can move at several meters in When a fault moves it can move at several meters in

a few a few secondsseconds



EarthquakeFaults

Rift valley


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Hot SpotsHot SpotsSome volcanoes are created away from plate Some volcanoes are created away from plate boundaries under places known as boundaries under places known as hot spots.hot spots.The heat pushes up mantle (forming an island The heat pushes up mantle (forming an island if in the middle of the ocean)if in the middle of the ocean)The Hawaiian islands are the great example of The Hawaiian islands are the great example of thisthis

– Main island of Hawaii is currently under a hot spot Main island of Hawaii is currently under a hot spot which is moving southeastwhich is moving southeast

– Other islands “behind” the hot spot include Oahu (3 Other islands “behind” the hot spot include Oahu (3 million years ago), Kauai (5 Mya), Midway (27 Mya)million years ago), Kauai (5 Mya), Midway (27 Mya)



Hawaii


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Plate Tectonics Through TimePlate Tectonics Through TimeSince we know how the continents are drifting at the Since we know how the continents are drifting at the present we can predict where they have been and present we can predict where they have been and where they are goingwhere they are goingAbout 200 million years ago all continents are together About 200 million years ago all continents are together as one called as one called PangeaPangeaBefore that the continents have moved all around: a Before that the continents have moved all around: a billion years ago Africa was located at the South Pole billion years ago Africa was located at the South Pole and Antarctica was near the Equatorand Antarctica was near the Equator

Earth’s activity is certainly a function of its size and distance Earth’s activity is certainly a function of its size and distance from the Sun and its rotation ratefrom the Sun and its rotation rate



drift

HistoryTerrestrial


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The EndThe End

© sierra college astronomy department 1 geology of the terrestrial planets terrestrial

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