GEOL 303 Exam #4

What is an asteroid?

• Small rocky/metal bodies in the Asteroid belt

• Circular orbit

Where is the Asteroid Belt located?

• Between Mars and Jupiter

What is a comet?

• Small bodies of frozen dust/ices/rock with elongated orbits

• Come from Kuiper Belt

Where is the Kuiper Belt located?

• Beyond the orbit of Neptune in the outer solar system

What are the tails of comets made of? Why?

• Sublimation = water going from solid straight to gas

• Tails made of ionizing gases and dust

What frozen gases are correlated with comets?

• H2O

• CO2

• CH4

• NH3

What is a meteoroid?

• Smaller interplanetary chunks of stone/metal

• Usually asteroids because comets will burn up

• In thermosphere

What is a meteor?

• Enters Earth’s atmosphere as a bright streak of light

• Burning up in mesosphere

What is a meteorite?

• A meteor that strikes Earth’s surface

Where does an airburst occur?

• Stratosphere

How old are meteorites?

• 4.6 byo

Types of meteorites

• Iron

• Stony

  • Most abundant

  • Silicates

• Stony-Iron

How often do 10 km object collide with Earth?

• 1/100 million years

How often do 1 km object collide with Earth?

• 1/1 million years

How often do 100 m object collide with Earth?

• 1/10,000 years

How often do 30m-50m object collide with Earth?

• 1/300 years

Hodges Meteorite

• Alabama, 1954

• Only person to survive direct impact of meteorite

Peekskill Meterorite

• New York, 1992

• Hit a lady’s new car

Chelyabinsk Meteorite

• Airbust

• Russia, 2013

• Asteroid 20m across, 10,000 metric tons, 40,000 mph

• Exploded 30km above Earth’s surface

• People got injured from glass breaking

Meteor Crater

• Arizona 50,000 years ago

• Iron meteorite, 50m diameter

Result of impact of very large object, 10km

• Massive quakes, tsunamis

• Shockwaves

• Firestorms

• Sun blocked

• Extinctions

• Climate Change

Excavation Stage of Impact

• Initial impact melts top layer and ejecting it into the air

  • Pushes down on ground and moves inward

End Excavation Stage of Impact

• Energy into the bottom of the crater rebounds up in the middle (central uplift), rim collapse

Modification Stage of Impact

• More rebound and rock

Final Crater after Impact

• Central uplift,

• Melt layer covered by breccia

• Marginal collapse zones

• Ejecta layers

What protects us from most space impacts?

• Earth’s atmosphere

Best strategy to avert space impacts?

• Detection and Diversion

K-T Impact

• End of dinosaurs

• 65 mya

• 10 km asteroid

• Yucatan

• 200km crater

  • Chicxulub Crater

K-T boundary

• Enriched with iridium

  • Common in meteorites

• Shocked quartz

• Blobs of melted rock

• Soot

  • Iridium is iron rich element

• Below boundary is fossil rich

Tunguska, Siberia Airbust

• Enormous shock/heat waves

• Forest flattened

• No crater

• Stony meteorite

  • ~50 m

• 1908

• Not that big of a deal because it landed in the middle of nowhere

  • If it had landed somewhere more populous, could have changed the course of history

How likely are you to die from an Asteroid Impact

• 1/700,000

What is a mass extinction?

• Catastrophic, widespread events killing many species in a short amount of geologic time

Causes of mass extinction?

• Plate tectonics

• Volcanism

  • Can put CO2 into the atmosphere

    • Warming the planet

  • Higher amounts of sulfur dioxide,

    • Cools the atmosphere

• Climate change

• Biologic

  • Natural selection

• Impact

• Cosmic Radiation

When was the Pre-Cambrian?

• 4.6 by - 540 my

When was the Palaeozoic?

• 540 my - 250 my

When was the Mesozoic?

• 250 my - 65 my

When was the Cenozoic?

• 65 my - present

What is a fossil?

• Ancient organisms petrified in sedimentary rock

Fossil Record

• Appearance of life forms and their disappearance

• Diversity increased

The Permian/Triassic Extinction

• “The Great Dying”

• Largest mass extinction

• No oxygen in the oceans, buried oxygen with chemical reactions

  • 90% of everything in the ocean died

• 250 mya

• Siberian basalt traps

  • Giant eruptions for hundreds of years

    • Low viscosity flow for many years, mafic magma

• Pangea

• Ocean warming

• Ocean shelf collapse

  • Lowering of sea level

• Release of H2S

K-T Extinction

• Triassic-tertiary extinction

• Deecan Traps, India

  • Gigantic flood basalts

  • Global climate change

• Marine regression

  • Sea level fall

  • Kills marine communities on shelves

  • Gravitational collapse of seafloor

  • Sea level changes

• Asteroid impacts

• 70-75% of all species died

Cretaceous (late mesozoic) Paleogeography

• Marine regression

• Cooling climate

• Flood basalts

• Plant life reduced

Dinosaurs

• Land dwellers

• Bird-like animals

• 140 mt

• Extinct from KT

What survived the KT extinction

• Mammals

• Birds

• Insects

• Flowering plants

Where are most dinosaur fossils found?

• where the Great Western Interior Seaway used to be

  • Four corners, US Southwest

Late Permian Paleogeography

• Pangea - loss of sea shelves

• Siberian flood basalst

  • Volcanic gases

• Ocean warming

• Arid conditions on Pangea due to size