© sierra college astronomy department 1 formation of the solar system

© Sierra College Astronomy Departmen© Sierra College Astronomy Departmentt

11

Formation of the Solar Formation of the Solar SystemSystem

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, noonNext week, Next 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.


33

Lecture 8a: The Formation of the Solar systemLecture 8a: The Formation of the Solar system

The Formation of the Solar SystemThe Formation of the Solar System

What properties must a planetary formation What properties must a planetary formation theory explain?theory explain?

1.1. It must explain the patterns of motion of the It must explain the patterns of motion of the present solar system (last week).present solar system (last week).

2.2. It must explain why planets form into 2 groups.It must explain why planets form into 2 groups.

3.3. It must explain the huge existence of asteroids It must explain the huge existence of asteroids and comets.and comets.

4.4. It must allow for possible exceptions to the rules.It must allow for possible exceptions to the rules.

The theory may be able to be used on other solar The theory may be able to be used on other solar systems in the Galaxysystems in the Galaxy


44


The Formation of the Solar SystemThe Formation of the Solar System

Evolutionary TheoriesEvolutionary TheoriesAll evolutionary theories have their start with All evolutionary theories have their start with Descartes’s whirlpool or vortex theory Descartes’s whirlpool or vortex theory proposed in 1644.proposed in 1644.Using Newtonian mechanics, Kant (in 1755) Using Newtonian mechanics, Kant (in 1755) and then Laplace (around 1795) modified and then Laplace (around 1795) modified Descartes’s vortex to a rotating cloud of gas Descartes’s vortex to a rotating cloud of gas contracting under gravity into a disk.contracting under gravity into a disk.The The Solar Nebular HypothesisSolar Nebular Hypothesis is an is an example of an evolutionary theory.example of an evolutionary theory.

SolarNebula


55


The Formation of the Solar SystemThe Formation of the Solar SystemCatastrophic TheoriesCatastrophic Theories

Catastrophic theoryCatastrophic theory is a theory of the formation is a theory of the formation of the solar system that involves an unusual of the solar system that involves an unusual incident such as the collision of the Sun with incident such as the collision of the Sun with another star.another star.The first catastrophic theory - that a comet pulled The first catastrophic theory - that a comet pulled material from the Sun to form the planets - was material from the Sun to form the planets - was proposed by Buffon in 1745.proposed by Buffon in 1745.Other Other close encounter hypothesesclose encounter hypotheses have been have been proposed too.proposed too.Catastrophic origins for solar systems would be Catastrophic origins for solar systems would be quite rare (relative to evolutionary origins) due to quite rare (relative to evolutionary origins) due to the unusual nature of the catastrophic incident.the unusual nature of the catastrophic incident.


66


Solar Nebula HypothesisSolar Nebula Hypothesis

Origin of the Solar NebulaOrigin of the Solar NebulaGalactic recyclingGalactic recycling– Most of the universe started as Hydrogen and Helium. Most of the universe started as Hydrogen and Helium.

All other heavy elements (loosely called “metals” by All other heavy elements (loosely called “metals” by astronomers) were formed in starsastronomers) were formed in stars

– When stars die they release much of the content into When stars die they release much of the content into spacespace

– While this has been going on for 4.6 billion years, only While this has been going on for 4.6 billion years, only 2% of all the have been converted to “metals”2% of all the have been converted to “metals”

Evidence from other gas cloudsEvidence from other gas clouds– All new systems that we can observed formed within All new systems that we can observed formed within

interstellar clouds, such as the Orion Nebulainterstellar clouds, such as the Orion Nebula

Galacticrecycling

Orion Nebula


77


Solar Nebula HypothesisSolar Nebula HypothesisTowards a Solar Nebula HypothesisTowards a Solar Nebula Hypothesis

A supernovae shock wave likely triggered the events A supernovae shock wave likely triggered the events which led to the birth of our solar systemwhich led to the birth of our solar systemThe nebular cloud collapsed due the force of gravity The nebular cloud collapsed due the force of gravity on the cloud. But the cloud does not end up on the cloud. But the cloud does not end up spherical (like the sun) because there are other spherical (like the sun) because there are other processes going on:processes going on:– Heating Heating – The cloud increases in temperature, converting – The cloud increases in temperature, converting

gravitational potential energy to kinetic energy. The sun would gravitational potential energy to kinetic energy. The sun would form in the center where temperatures and densities were the form in the center where temperatures and densities were the greatestgreatest

– SpinningSpinning – as the cloud shrunk in size, the rotation of the disk – as the cloud shrunk in size, the rotation of the disk increases (from the conservation of angular momentum).increases (from the conservation of angular momentum).

– FlatteningFlattening – as cloud starting to spin, collisions flattened the – as cloud starting to spin, collisions flattened the shape of the disk in the plane perpendicular to the spin axisshape of the disk in the plane perpendicular to the spin axis

Cloudcollapse2


88


Testing the ModelTesting the Model

If the theory is correct, then we should see If the theory is correct, then we should see disks around young starsdisks around young stars

Dust disksDust disks,, such as discovered around such as discovered around beta-Pictoris or AU Microscopii, provide beta-Pictoris or AU Microscopii, provide evidence that conditions for planet formation evidence that conditions for planet formation exist around many Sun-like stars.exist around many Sun-like stars.

AU Mircoscopii HD 141569A

Disks around other stars


1010


Solar Nebula HypothesisSolar Nebula HypothesisThe Formation of PlanetsThe Formation of Planets

As the solar nebula cooled and flattened into a disk some 200 AU As the solar nebula cooled and flattened into a disk some 200 AU in diameter, materials began to “freeze” out in a process called in diameter, materials began to “freeze” out in a process called condensation condensation (changing from a gas to a solid or liquid).(changing from a gas to a solid or liquid).The ingredients of the solar system consist of 4 categories (with % The ingredients of the solar system consist of 4 categories (with % abundance):abundance):

– Hydrogen and Helium gas (98%)Hydrogen and Helium gas (98%)– Hydrogen compounds, such as water, ammonia, and methane (1.4%)Hydrogen compounds, such as water, ammonia, and methane (1.4%)– Rock (0.4%)Rock (0.4%)– Metals (0.2%)Metals (0.2%)

Since it is too cool for H and He to condense, a vast majority of the Since it is too cool for H and He to condense, a vast majority of the solar nebula did not condensesolar nebula did not condenseHydrogen compounds could only condense into ices beyond the Hydrogen compounds could only condense into ices beyond the frost linefrost line, , which lay between the present-day orbits of Mars and which lay between the present-day orbits of Mars and JupiterJupiter

Frost line

categories


1111


Solar Nebula HypothesisSolar Nebula HypothesisBuilding the Terrestrial PlanetsBuilding the Terrestrial Planets

In the 1940s, Weizsächer showed that In the 1940s, Weizsächer showed that eddies would formeddies would form in a in a rotating gas cloud and that the eddies nearer the center would be rotating gas cloud and that the eddies nearer the center would be smaller.smaller.Eddies condense to form particles that grow over time in a Eddies condense to form particles that grow over time in a process called process called accretionaccretion.. Materials such and rock and metal Materials such and rock and metal (categories #3 and #4).(categories #3 and #4).These accreted materials became These accreted materials became planetesimalsplanetesimals which in turn which in turn sweep up smaller particles through collision and gravitational sweep up smaller particles through collision and gravitational attraction.attraction.These planetesimals suffered gravitational encounters which These planetesimals suffered gravitational encounters which altered their orbits caused them to both coalesce and fragment. altered their orbits caused them to both coalesce and fragment. Only the largest planetesimals grew to be full-fledged planets.Only the largest planetesimals grew to be full-fledged planets.Verification of this models is difficult and comes in the form of Verification of this models is difficult and comes in the form of theoretical evidence and computer simulations.theoretical evidence and computer simulations.

Jovianplanetesimals

planetesimals

Mixed rockmeteorite


1212



Building the Jovian PlanetsBuilding the Jovian Planets

Planetesimals should have also grown in the Planetesimals should have also grown in the outer solar system, but would have been outer solar system, but would have been made of ice as well as metal and rock.made of ice as well as metal and rock.But Jovian planets are made mostly of H and But Jovian planets are made mostly of H and He gas…He gas…The gas presumably was captured by these The gas presumably was captured by these ice/rock/metal planetesimals and grew into ice/rock/metal planetesimals and grew into the Jovian planets of today.the Jovian planets of today.


1313


Solar Nebula HypothesisSolar Nebula HypothesisAA Stellar wind Stellar wind is the flow of nuclear is the flow of nuclear particles from a star.particles from a star.Some young stars exhibit strong stellar Some young stars exhibit strong stellar winds. If the early Sun went through such a winds. If the early Sun went through such a period, the resulting intense period, the resulting intense solar windsolar wind would have swept the inner solar system would have swept the inner solar system clear of volatile (clear of volatile (low densitylow density) elements, ) elements, molecules and compounds.molecules and compounds.The giant planets of the outer solar system The giant planets of the outer solar system would then have collected these outflowing would then have collected these outflowing gases.gases.


1414


Solar Nebula HypothesisSolar Nebula HypothesisAn object shrinking under the force of gravity An object shrinking under the force of gravity heats up. High temperatures near the newly heats up. High temperatures near the newly formed Sun (formed Sun (protosunprotosun) will prevent the ) will prevent the condensation of more volatile (low density) condensation of more volatile (low density) elements. Planets forming there will thus be elements. Planets forming there will thus be made of nonvolatile, dense material.made of nonvolatile, dense material.

Farther out, the eddies are larger and the Farther out, the eddies are larger and the temperatures cooler so large planets can form temperatures cooler so large planets can form that are composed of volatile elements (light that are composed of volatile elements (light gases).gases).

PlanetBuilding


1515


Solar Nebula HypothesisSolar Nebula HypothesisProblem:Problem: The total angular momentum of The total angular momentum of the planets is known to be greater than that the planets is known to be greater than that of the Sun, which should not occur according of the Sun, which should not occur according to conservation laws to conservation laws (i.e. the present Sun is (i.e. the present Sun is spinning too slowly).spinning too slowly).Solution:Solution: As the young Sun heated up, it As the young Sun heated up, it ionizedionized the gas of the inner solar system. the gas of the inner solar system. – The Sun’s magnetic field then swept through the The Sun’s magnetic field then swept through the

ions in the inner solar system, causing ions to ions in the inner solar system, causing ions to speed up.speed up.

– As per Newton’s third law, this transfer of energy As per Newton’s third law, this transfer of energy to the ions caused the to the ions caused the Sun to slow its rate of Sun to slow its rate of rotation. rotation.


1616



Explaining Other CluesExplaining Other Clues

Over millions of years the remaining Over millions of years the remaining planetesimals fell onto the moons and planetesimals fell onto the moons and planets causing the cratering we see today. planets causing the cratering we see today. This was the period of This was the period of heavy bombardmentheavy bombardment..

Comets are thought to be material that Comets are thought to be material that coalesced in the outer solar system from the coalesced in the outer solar system from the remnants of small eddies.remnants of small eddies.


1717



The formation of Jovian planets and its The formation of Jovian planets and its moons must have resembled the moons must have resembled the formation of the solar system. Jupiter formation of the solar system. Jupiter specifically: specifically: – Moons close to Jupiter are denser and Moons close to Jupiter are denser and

contain fewer light elements; contain fewer light elements;

– Moons farther out decrease in density and Moons farther out decrease in density and increase in heavier elements. increase in heavier elements.


1818


The Exceptions to the RuleThe Exceptions to the Rule

Captured MoonsCaptured Moons – satellites which go the – satellites which go the opposite way were likely captured. Most of opposite way were likely captured. Most of these moons are small are lie far away from these moons are small are lie far away from the planet.the planet.

Giant impactsGiant impacts – may have helped form the – may have helped form the Moon and explain the high density of Mercury Moon and explain the high density of Mercury and the Pluto-Charon system. Furthermore, and the Pluto-Charon system. Furthermore, the unusual tilts of Uranus and Venus can the unusual tilts of Uranus and Venus can also be explained by giant impacts. also be explained by giant impacts.

Giant impactMoon

Solar Nebula TheorySummary

Phobos Deimos


1919


Solar System DestinySolar System DestinyThe nebular hypothesis accounts for all major The nebular hypothesis accounts for all major features in the solar systemfeatures in the solar systemIt does not account for It does not account for everythingeverything, however, howeverIt probably took about a few tens of million of years, It probably took about a few tens of million of years, about 1% of the current age of the solar systemabout 1% of the current age of the solar systemThe solar system was probably not completely The solar system was probably not completely predestined from the collapse of the solar nebula, predestined from the collapse of the solar nebula, though the initial were orderly and inevitablethough the initial were orderly and inevitableThe final stage of accretion and giant impacts were The final stage of accretion and giant impacts were fairly random in nature and made our solar system fairly random in nature and made our solar system uniqueunique


2020


RadioactivityRadioactivity


Certain isotopes (elements which contain differing Certain isotopes (elements which contain differing number of neutrons) are not stable and will decay number of neutrons) are not stable and will decay into two or more lighter elementsinto two or more lighter elements

The time it takes for half of a given isotope to decay The time it takes for half of a given isotope to decay is called the is called the half-lifehalf-life

By noting what percentage a rock (or human body) By noting what percentage a rock (or human body) has left of a radioactive element can enable us to has left of a radioactive element can enable us to estimate the age of that object. This process is called estimate the age of that object. This process is called radioactive dating. radioactive dating. See Mathematical Insight 8.1See Mathematical Insight 8.1

Half-lifeK-40

PeriodicTable

Half-life 2


2121



Radioactivity - examplesRadioactivity - examplesPotassium-40 decays into Argon-40 with a half-life of Potassium-40 decays into Argon-40 with a half-life of 1.25 billion years1.25 billion years– Since Argon-40 is an inert gas, it is very unlikely to have formed Since Argon-40 is an inert gas, it is very unlikely to have formed

inside a rock as the solar nebula condensed, so it must have inside a rock as the solar nebula condensed, so it must have formed via decayformed via decay

Uranium-238, after a series of Uranium-238, after a series of decays, turns into Lead-decays, turns into Lead-206 with half-life of 4.5 billion years206 with half-life of 4.5 billion years– Lead and Uranium have very different chemical behavoirsLead and Uranium have very different chemical behavoirs– Some minerals have nearly no lead Some minerals have nearly no lead to begin withto begin with, so when , so when

uranium is mixed with lead, we can assume that the lead formed uranium is mixed with lead, we can assume that the lead formed via decayvia decay

Half-lifeK-40

PeriodicTable


2222




The general formula for the age of a radioactive The general formula for the age of a radioactive material is material is (see Mathematical Insight 8.1):(see Mathematical Insight 8.1):

Half-lifeK-40

PeriodicTable

Half-life 2

10

10

log

1log

2

half

current amountoriginal amount

t t


2323



Earth rocks, Moon rocks, and meteoritesEarth rocks, Moon rocks, and meteorites

The oldest Earth rock date back to 4 billion years The oldest Earth rock date back to 4 billion years and some small grains go back to 4.4 billion years. and some small grains go back to 4.4 billion years. Moon rock brought back from the Apollo mission Moon rock brought back from the Apollo mission date as far back as 4.4 billion years.date as far back as 4.4 billion years.– These tell us when the rock solidified, not when the These tell us when the rock solidified, not when the

planet formedplanet formed

The oldest meteorites, which likely come form The oldest meteorites, which likely come form asteroids, are dated at 4.55 billion years, marking asteroids, are dated at 4.55 billion years, marking the time of the accretion of the solar systemthe time of the accretion of the solar system

Half-life 2


2424

Lecture 8b: Terrestrial Geology BasicsLecture 8b: Terrestrial Geology Basics

Earth’s Structure & CompositionEarth’s Structure & CompositionThe Interior of the Earth (The Interior of the Earth (overall density = 5.5 g/cmoverall density = 5.5 g/cm33))

Earth’s interior is determined by analyzing travel times Earth’s interior is determined by analyzing travel times of two types of waves generated by earthquakes.of two types of waves generated by earthquakes.Earth’s interior is made up of three layers:Earth’s interior is made up of three layers:– CrustCrust is the thin (<100 km) outermost layer of the Earth and is the thin (<100 km) outermost layer of the Earth and

has a density of has a density of 2.5–3 g/cm2.5–3 g/cm33. . – MantleMantle is the thick (2,900 km), solid layer between the crust is the thick (2,900 km), solid layer between the crust

and the Earth’s core. Density of the mantle is and the Earth’s core. Density of the mantle is 3–9 g/cm3–9 g/cm33. The . The crust “floats” on top of the mantle. crust “floats” on top of the mantle.

– CoreCore is the central part of the Earth, composed of a is the central part of the Earth, composed of a solid inner solid inner corecore and a and a liquid outer coreliquid outer core. Density of the core ranges from . Density of the core ranges from 9–13 g/cm9–13 g/cm33 and is probably composed of iron and nickel. and is probably composed of iron and nickel.

Increasing density trend is called Increasing density trend is called differentiationdifferentiation - - sinking of denser materials toward the center of planets sinking of denser materials toward the center of planets or other objects.or other objects.

interior

Diff

EarthQ

EarthQ2

Terr.insides


2525


Earth’s Structure & CompositionEarth’s Structure & Composition

Layering by StrengthLayering by StrengthMost of the Earth is not molten and most of the Most of the Earth is not molten and most of the lava from volcanoes rises upward from a lava from volcanoes rises upward from a narrow region of the mantle which is partially narrow region of the mantle which is partially molten.molten.The shape of a planet is determined by the The shape of a planet is determined by the strength and fluidity of the inside as well as the strength and fluidity of the inside as well as the strength of gravitystrength of gravity– Large worlds (> 500 km diameter) are roundLarge worlds (> 500 km diameter) are round– Small worlds are irregular in shapeSmall worlds are irregular in shape

The crust and the top part of the mantle is The crust and the top part of the mantle is relatively cool region of rock called the relatively cool region of rock called the lithosphere lithosphere that floats on the rest of the that floats on the rest of the mantle.mantle.

Shapes

Terr.insides


2626


Causes of Geological ActivityCauses of Geological Activity

Geological ActivityGeological Activity describes how much describes how much ongoing change occurs on the surface of ongoing change occurs on the surface of a solar system bodya solar system body

Interior heat is the primary driver for Interior heat is the primary driver for geological activitygeological activity

But how do interior heat up and cool off?But how do interior heat up and cool off?


2727


Causes of Geological ActivityCauses of Geological Activity

How planets heat upHow planets heat upHeat of accretionHeat of accretion– Energy brought from afar from colliding planetesimals – potential energy Energy brought from afar from colliding planetesimals – potential energy

converted into kinetic energyconverted into kinetic energyHeat of differentiationHeat of differentiation– As the planet redistributes its mass and denser material sinks towards As the planet redistributes its mass and denser material sinks towards

the core gravitational potential energy is converted to thermal energy via the core gravitational potential energy is converted to thermal energy via frictionfriction

Heat from radioactive decayHeat from radioactive decay– Decay from radioactive materials heats up the interior as some of the Decay from radioactive materials heats up the interior as some of the

nuclear decay energy ( nuclear decay energy ( E = mcE = mc22 ) gets transferred to thermal energy ) gets transferred to thermal energy

Note: the first of these two tend to happen early in a planet’s history Note: the first of these two tend to happen early in a planet’s history while the last (radioactive decay) happens throughout the history of while the last (radioactive decay) happens throughout the history of the planet, but is strongest at the beginning of the formation of the the planet, but is strongest at the beginning of the formation of the planet. Radioactive decay likely contributes several times more planet. Radioactive decay likely contributes several times more energy over the life of the planet than does accretion and energy over the life of the planet than does accretion and differentiation.differentiation.

Heatsources


2828

How Interiors Cool Off:How Interiors Cool Off:ConductionConduction– Transfers occurs between atomsTransfers occurs between atoms– Examples: metal rod in fire, Earth’s core and lithosphereExamples: metal rod in fire, Earth’s core and lithosphere

ConvectionConvection– Warmer (less dense) air rises and carries energy into cooler (denser) regionsWarmer (less dense) air rises and carries energy into cooler (denser) regions– Requires large temperature Requires large temperature gradientgradient– Examples: Lava lamp, Earth atmosphere and mantle, Sun’s outer layersExamples: Lava lamp, Earth atmosphere and mantle, Sun’s outer layers

RadiationRadiation– Photons directly transfer energyPhotons directly transfer energy– Less efficient in high density situationsLess efficient in high density situations– Photons take ~ 200,000 years to get of Sun.Photons take ~ 200,000 years to get of Sun.– Examples: Heat lamp, Earth’s surface, Sun’s interiorExamples: Heat lamp, Earth’s surface, Sun’s interior

ThreeTypes

DemoLava lamp

Lecture 8b: Terrestrial Geology BasicsLecture 8b: Terrestrial Geology BasicsTransfer of EnergyTransfer of Energy

Earthcooling


2929

How the Earth moves energy from the core to How the Earth moves energy from the core to the surface:the surface:Convection is the most important process in Convection is the most important process in the Earth’s deep interiorthe Earth’s deep interior– The ongoing process of transferring heat upward The ongoing process of transferring heat upward

creates creates convection cellsconvection cells– Ongoing mantle convection goes at the rate of 1 Ongoing mantle convection goes at the rate of 1

cm/year: It would take about 100 million years to cm/year: It would take about 100 million years to move the mantle from the base to the topmove the mantle from the base to the top

At the lithosphere, conduction is probably the At the lithosphere, conduction is probably the most important processmost important process

Lecture 8b: Terrestrial Geology BasicsLecture 8b: Terrestrial Geology BasicsTransfer of EnergyTransfer of Energy

Earthcooling


3030

A small object cools more quickly than a large A small object cools more quickly than a large objectobjectSo size is the most important factor in So size is the most important factor in planetary coolingplanetary coolingThis can be seen in the terrestrial worlds:This can be seen in the terrestrial worlds:– Earth and Venus: still very active.Earth and Venus: still very active.– Mars: Activity in the past, but mostly dead now.Mars: Activity in the past, but mostly dead now.– Moon and Mercury have been dead for 3 billion Moon and Mercury have been dead for 3 billion

years or so.years or so.

Lecture 8b: Terrestrial Geology BasicsLecture 8b: Terrestrial Geology BasicsPlanetary SizePlanetary Size

Earthcooling


3131


Earth’s MagnetosphereEarth’s Magnetosphere

Earth’s Magnetic FieldEarth’s Magnetic FieldA A magnetic fieldmagnetic field is a region of space where is a region of space where magnetic forces can be detected. The region magnetic forces can be detected. The region around a planet is called a around a planet is called a magnetospheremagnetosphereEarth’s magnetic poles are not located at its Earth’s magnetic poles are not located at its poles of rotation. The location of the poles of rotation. The location of the magnetic poles changes with time.magnetic poles changes with time.Dynamo effectDynamo effect is the model that explains is the model that explains the Earth’s and other planets’ magnetic the Earth’s and other planets’ magnetic fields as due to currents within a fields as due to currents within a liquidliquid iron iron core core and a rapidly spinning planetand a rapidly spinning planet..

BasicEarth Mag field

magnetosphere

Demo

Magnetic field

dynamo Earthdynamo


3232


Earth’s MagnetosphereEarth’s Magnetosphere

TheThe Van Allen belts Van Allen belts are doughnut-shaped are doughnut-shaped regions composed of charged particles regions composed of charged particles (protons & electrons) emitted by the Sun & (protons & electrons) emitted by the Sun & captured by the magnetic field of the Earth.captured by the magnetic field of the Earth.AurorasAuroras result from disturbances in the result from disturbances in the Earth’s magnetic field that cause some of Earth’s magnetic field that cause some of the particles to follow the magnetic field lines the particles to follow the magnetic field lines down to the atmosphere, where their down to the atmosphere, where their collisions with atoms of the air cause it to collisions with atoms of the air cause it to glow.glow. Aurora

Aurora from the Ground


3434

Aurora From Space


3535


Shaping the EarthShaping the Earth

There are 4 processes which shape the There are 4 processes which shape the virtually all features on Earthvirtually all features on Earth

1.1. Impact CrateringImpact Cratering Bowl shaped from asteroids or meteorsBowl shaped from asteroids or meteors

2.2. VolcanismVolcanism Eruption of lava from planet’s interiorEruption of lava from planet’s interior

3.3. TectonicsTectonics Disruption of planet’s surface by internal forcesDisruption of planet’s surface by internal forces

4.4. ErosionErosion Wearing down or building of geological Wearing down or building of geological

features by wind, water, ice etc…features by wind, water, ice etc…


3636


Impact CrateringImpact Cratering

As a general rule the craters made by meteors As a general rule the craters made by meteors are 10 times bigger than the impactor and 10-are 10 times bigger than the impactor and 10-20% as deep as the crater is wide.20% as deep as the crater is wide.Most impacts happened very early in the history Most impacts happened very early in the history of the solar systemof the solar systemThe most prominent impact crater on Earth is The most prominent impact crater on Earth is Meteor Crater near Winslow, Arizona (only Meteor Crater near Winslow, Arizona (only 50,000 years ago).50,000 years ago).Many of the craters on the Earth have been Many of the craters on the Earth have been wiped out by erosion processeswiped out by erosion processes– Not true for Moon and MercuryNot true for Moon and Mercury

Meteorcrater

impact


3737


VolcanismVolcanism

Volcanism occurs when underground molten Volcanism occurs when underground molten rock finds it way through the lithosphere. This is rock finds it way through the lithosphere. This is due for 3 reasons:due for 3 reasons:– Molten rock is generally less dense than solid rockMolten rock is generally less dense than solid rock– Most of the Earth’s interior is not molten and it Most of the Earth’s interior is not molten and it

requires a chamber of molten rock to be squeezed requires a chamber of molten rock to be squeezed up the surfaceup the surface

– Molten rock often has gas inside of it, leading to Molten rock often has gas inside of it, leading to dramatic eruption and to dramatic eruption and to outgassingoutgassing

The most common gasses released are water The most common gasses released are water vapor, carbon dioxide, nitrogen, and sulfur vapor, carbon dioxide, nitrogen, and sulfur gasses (Hgasses (H22S or SOS or SO22))

RiftSubduc

Drift

Plates


3838


Plate TectonicsPlate Tectonics

Plate TectonicsPlate TectonicsAlfred 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.Rift zoneRift zone is a place where tectonic plates is a place where tectonic plates are being pushed apart, normally by molten are being pushed apart, normally by molten material being forced up out of the mantle.material being forced up out of the mantle.

Subduction ZoneSubduction Zone is where two plates are is where two plates are forced together.forced together.

RiftSubduc

Drift

Plates

tectonics


3939


ErosionErosion

The surface of the Earth is changed by The surface of the Earth is changed by erosionerosion, the processes that break down or , the processes that break down or transport rock through the action of ice, liquid, transport rock through the action of ice, liquid, or gasor gas– Valleys shaped by glaciersValleys shaped by glaciers– Canyons carved by riversCanyons carved by rivers– Shifting of sand dunes by the airShifting of sand dunes by the air

Erosion can pile up sediments into layers called Erosion can pile up sediments into layers called sedimentarysedimentary rocks (Ex. Grand Canyon) rocks (Ex. Grand Canyon)The Earth has the most erosion of any The Earth has the most erosion of any terrestrial planetterrestrial planet

Erosion


4040

The number of craters in a given region The number of craters in a given region can tell one the age of the planet/moon can tell one the age of the planet/moon since the last major change on surfacesince the last major change on surface– Does not necessarily indicate formation ageDoes not necessarily indicate formation age

Erosion from wind, water, and lava will Erosion from wind, water, and lava will wipe out craters in a given regionwipe out craters in a given region– This led to determining the development of This led to determining the development of

different parts of the planet/moondifferent parts of the planet/moon


Age of surfaces

Craters


4141

The EndThe End

© sierra college astronomy department 1 formation of the solar system

Documents

solar system slide

solar systems

solar nebula slide

present solar system

solar nebular hypothesis

planetary formation

evolutionary theory

vortex theory