GEO 1306 Exam 2 - Petsios

Catastrophic events in human history

2011 Tohoku Earthquake and Tsunami, 2005 hurricane Katrina, 2004 Indian ocean tsunami, 1980 Mt. St. Helens Eruption, 1883 Krakatoa eruption, Destruction of Pompeii and Santorini,(~1500-2000 years ago)

Catastrophic events in geologic time

Chicxulub impact, Yucatan impact

Chicxulub impact

ended the Age of the Dinosaurs

Asteroid impact in Yucatan ~65 million years ago

Caused extinction of dinosaurs and other organisms

James Hutton

"father of modern geology" in 1800's, Postulated that stratigraphic layers pile up very slowly over many years

Charles Lynell

proposed the concept of uniformitarianism

uniformitarianism

geologic processes that occurred in the past can be explained by current processes

North American Plate movement

2.3 cm/year

Intrusive igneous rocks form

thousands to millions of years

Extrusive igneous rocks form

minutes to days

Sediment accumulation (Mississippi river delta)

2.5 - 4cm/year

Sediment accumulation (bottom of the ocean)

<2cm/1000 years

Himalayan mountain growth

1cm/year

Himalayan mountain erosion

1.5mm/year

Relative age

The age of a rock compared to the ages of rock layers

Absolute age

the number of years since the rock formed

Measure relative age

Apply stratigraphic principles

Measure absolute age

measuring radioactive decay

Radioactive decay

Expel particles or energy to become more stable

Parent atom

original unstable atom

Daughter atom

stable atom after decay

Beta decay

neutron converts to proton

Half-life

time it takes for ½ of remaining parent particles to decay

1 half life

5730 years

2 half lives

11,460 years

Possible to calculate how many half-lives have passed if

Amount of parent atoms left is known, decay rate is known (constant)

Radiocarbon dating

determining age by comparing the amount of carbon-14 to the amount of carbon-12 in a sample

Eon

the largest division of geologic time

Hadean Eon

Earliest Eon, 4.6 - 4 billion years ago. Earth's surface still molten

Archean Eon

4 - 2.5 billion years ago, Earth's surface cooled and solidified, formation of continents, start of plate tectonics, Oceans form, likely first single-celled life

Proterozoic Eon

2.5 - 0.55 billion, oxygenated atmosphere forms, First multicellular life

Phanerozoic Eon

550 million - today, most of the fossil record

Hades

Greek underworld

Archaea

the beginning

1. Protero 2. zoic

first life

1. Phanero 2. zoic

visible life

The Cambrian

first period of phanerozoic

Precambrian

before Earth's history, 4.5 - 0.5 billion years ago

Formation of our solar system

Dust and gas coalesce from stellar nebula under the influence of gravity

Age of our solar system (radiometric data from meteorites

between 4.53 and 4.58 billion years

Gravitational accretion

object with mass attract other object with mass

Earth is mostly comprised of

Felsic and Metals/Mafic rocks

Differentiation of Earth's layers occurred

during formation while Earth was still molten

Earth's Magnetic Field

Produced by the spinning of Earth's liquid outer core

Giant Impact Hypothesis

planetesimal the size of Mars hit Earth

Theia

hypothetical planetesimal

Moon is composed of mostly

felsic minerals

The Heavy Bombardment Phase

Period of intense impacts in early solar system.

Age of the Earth

4.5 billion years

Age of moon rock

4.6 billion years

Oldest rocks on Earth

3.8 - 4.28 billion (Canada)

4.4 billion (Australia)

Eon that Earth formed and end of heavy bombardment stage

The Hadean Eon

Continental crust composition

felsic

Oceanic crust composition

mafic

Cratons (archean crust)

the stable interior of the continents

Isua Greenstone, Greenland (pillow basalts)

Metamorphosed igneous and sedimentary rock, 3.8 billion years

Gneiss

high grade metamorphosed igneous or sedimentary rock

Greenstone Belts

highly metamorphosed mafic, ultramafic, and sedimentary rocks

Archean Cratons

Composed of granite-gneiss terranes and greenstone belts

how much of Earth's surface is covered by water

70%

Dissolved ions account for

3.5% in ocean water

35 g "salts" per

Liter of H2O

Ca+2 ion

important for making CaCO3 (limestone)

Source of dissolved ions

Continental weathering

Chemical erosion of rocks on the continents

Ocean water freezes

-2 degrees C

Ocean water boils

101 degrees C

Sea surface temperatures

17 degrees C (63F) average

World surface temper temperatures

15 degrees C (58F) average

Evidence of Early Water

Pillow basalts (can only happen if formed in liquid water)

Source of Water (terrestrial)

H2O came out of early volcanoes as water vapor

Source of Water (extraterrestrial)

Icy comets

Halley's Comet

80% H2O ice

Goldilocks Zone Hypothesis

habitable area from the sun

Atmosphere composition

78% N2, 21% O2, 1% Ar, 0.04% CO2

Where did the nitrogen come from

built up from years of volcanic gas

Where did the oxygen come from

photosynthesis

stromatolites

fossils made up of microorganisms

Isua stromatolites age

3.8 billion years

Evidence for oxygen

Oxidation, Banded iron formations

% of oxygen in todays oceans

1% dissolved oxygen

Banded iron formations

Made of iron oxides, Needs free oxygen

Steady State

energy in is the same as energy out

rising temps

If more energy is entering the system than is leaving the system

falling temps

If more energy is leaving the system than is entering the system

Solar Luminosity (energy in)

how much energy is emitted from the sun

Solar Insolation (energy in)

how much energy reaches Earth

Eccentricity

standard of Earth's orbit

Earth's orbit changes

every 100,000 years

Greenhouse effect (energy in)

how much energy is kept on Earth

Black body radiation (energy out)

heat radiated into space as infrared radiation

Icehouse (Earth's current state)

stable ice at poles

Greenhouse

no stable ice at poles

How do we know past temps

Stable Oxygen Isotopes, Fractionation

Stable Oxygen Isotopes

doesn't decay

Fractionation

giving radiation in small, repeated doses