Exam 2 Notes Comp

Moon Size

Our moon is quite big for a planet of Earth's size, about 1/4th of Earth’s size

Effects of Moon on Earth

The gravity of the Moon and the Sun pull the ocean towards them, which creates tides. Pull is stronger when sun and moon work together

Planetary Fission

19th-century hypothesis where the earth and moon were a single body at 4.6Ga and rotation caused a chunk of earth to detach. Not physically possible

Capture Hypothesis

The Moon formed elsewhere and was captured by Earth’s gravity (much like the Moons of Mars), Earth could not catch an object so big smoothly

Co-Accretion Hypothesis

the Earth and the Moon formed at the same time, and the Moon accreted from dust and meteorites orbiting around early Earth. works with big planets, but earth didn't have enough gravity to create this

Moon Age

Rocks sampled during Apollo missions in 60’s & 70’s provide moon age - 4.4 Ga, which is during the first 50-100 million years of the Solar System. Moon and Earth ~same age

Moon Rocks

Surface is all igneous rock, no transformed through sedimentary processes, no metamorphic rock, as moon hasn't been geologically active in a long time

Moon vs Earth

Earth is denser, has more iron in core, and more diverse crust. The moon has no minerals that include water in their crystal structure

Big Thwack Hypothesis

Large planetesimal (the size of Mars) called Theia smashed into Early Earth, impact caused Theia and Earth’s surface to melt and the debris re-accreted around the Earth as the Moon

Support for Big Thwack

Explains density difference, iron abundance, similarities in composition (same isotopic oxygen signature), tilt of earths axis, reproducible on models, and explains why we only see one side of moon

Post Thwack

Moon looked 16x bigger than sun, constant eclipses, Earth was spinning very fast, and a mile-high magma bulge was created as the moon orbited

Moon & Earth Spin

As the moon moves farther away the earth spins more slowly, connected relationship

The Magnetosphere

Earth’s spinning liquid iron outer core generates a magnetic field that shields from charged particles, keeps atmosphere intact, and protects from wavelengths of solar radiation and plasma bursts

Earth's Modern Atmosphere

Cyanobacteria would arise and produce enough oxygen for it to be a significant portion of the atmosphere, creating an atmosphere similar to what we have today.

Earth's First Atmosphere

primarily composed of hydrogen and helium, which eventually escaped into space because Earth's gravity is not strong enough to hold them.

Earth’s Second Atmosphere

Prebiotic, created from volcanic gases and was mostly carbon dioxide, water vapor, and nitrogen. The water would have precipitated to form Earth's oceans.

Old Water Hypothesis

water was delivered to early Earth by icy comets and asteroids

Current Water Hypothesis

Earth’s water was extracted from hydrogen and oxygen-rich minerals in the mantle and erupted to the surface as water vapor via volcanoes

Waterworld

Early Earth had a basaltic crust covered completely by ocean, no continents

Volcanic Island Arcs

Ocean-to-ocean continental subduction interactions made island arcs, first dry land after waterworld, still primarily basalt

Greenstone Belts

Sedimentary basins compressed into one another with granite and gneiss in between, subduction processes push volcanic arcs and basins into one another, tectonics cause metamorphism, erosion bevels the topographic surface

Cratons

Large, stable interiors of continents that contain the oldest rocks on Earth and provide the best evidence for conditions on early Earth

The Inner Rocky Planets

Mercury, Venus, Earth, Mars and Ceres (a dwarf planet in the asteroid belt)

Extraterrestrial Origins

Life may have originated somewhere else and been transported here via meteorite, would have to survive many different types of intense conditions

Asteroid Life?

Samples from Bennu found ammonia, an essential building block of the amino acids that form proteins in life, and all five nucleobases that make up DNA and RNA

Shallow Water Origins

The primary hypothesis for a long time, early earth history there were shallow oceans that had the ingredients for life, maybe triggered by things like lightning strikes

Miller Urey Experiments (1953)

Mixed gases, water, and an electric spark to produce amino acids and nucleotide bases (aka, the “building blocks” of life), mimics the conditions in ancient Earth’s shallow oceans. Did not actually create new life

Deep Water Origins

The extreme temperature gradient (hot vent water + cold ocean floor) is capable of facilitating complex chemical reactions, leading hypothesis for life origins

In between Origins

Still don't know where life originated, could be in between shallow and deep. There are vent systems in shallower water that also have weird chemistry

Age of Life

Molecular clock evidence points to life evolving somewhere around 4 billion years ago - farther back than we have fossil evidence for. Do have fossils that date over 3.5 Ga

Apex Chert Microfossils

Possible fossilized cyanobacteria from Australia, 3.5 Ga. Might not be actual fossilized life

Ancient Seeps

Possibly oldest life every found - 3.77 - 4.28 Ga. From greenstone belts in canadian shield

Cellular “shadows”

Thought to be individual cells preserved in the rock. 3.4 Ga in Australia

Stromatolites

Calcareous mounds built up by layers upon layers of bacterial mats, rare because algal mats are eaten before they can build up

Banded Iron Formations (BIFs)

layered sedimentary rocks composed of alternating thin bands of red iron-rich minerals (magnetite or hematite) and black silica-rich minerals (chert or jasper)

BIF Formation

Before atmospheric oxygen, iron remained dissolved in ocean water (no BIFs) After oxygenation, iron could precipitate out of solution as hematite and other iron oxides, forming BIFs

Oxygenation of Atmosphere

Can look at BIF’s to see amount of oxygen in atmosphere, Whifts of O2 at 3-2.5 Ga, at 2.5 Ga there was a big shift and global deposition of banded iron, O2 bumps to modern day amounts during snowball earth

Carbon Cycle

Continuous process by which carbon atoms travel between the atmosphere, Earth’s oceans, soil, rocks, and living organisms. Most disrupted by changes in eruptions, chem weathering, and carbonate rock formations

Greenhouse Effect

If you add carbon to atmosphere, planet gets hotter and vice versa, moderates temp fluctuations on earth

Snowball Earth

Two events during the cryogenian, lasted 30 million years

Albedo

Reflectivity of the surface of a planet - Ocean is dark and absorbs, Ice is light and reflects

Runaway Albedo

Triggered by Rodinia breaking up which caused high erosion - drawdown of atmospheric co2, got colder and polar ice caps grew larger

Snowball Deposits

Easily recognized by a distinct package of sedimentary rocks that include glacial till, ice-rafted debris, and cap carbonates. Found over entire planet

Glacial Till (B)

Very poorly sorted sediment deposited by glaciers as they excavate valleys. Large cobbles will have striations from being dragged. Found in low latitudes where glaciers shouldn’t be

Ice Rafted Debris (M)

Large drop stones found in fine-grained marine sediment. Caused by ice sheets melting and dropping stones. Found in low latitudes where glaciers shouldn’t be

Cap Carbonates (T)

Limestone deposit caused by rapid influx of carbon dioxide and other greenhouse gases into the ocean after the ice sheets melted, form in shallow, warm oceans

End of Snowball Earth

Ice sheet acts as barrier between the atmosphere, ocean, and land, shuts down carbon cycle and allows a buildup of greenhouse gas in atmosphere as volcanoes release CO2. Eventually triggers greenhouse effect and warms planet

Darwin’s Dilemma

If you are limited by looking at body fossils that are easily accessable/found, it seems like complex animals just magically appeared in the cambrian which is impossible

Eukaryogenesis

A symbiotic relationship between archaea and bacteria likely produced the first eukaryotic cells, between approximately 1.8 and 2.7 Ga

FMCA

first mitochondrial common ancestor

FECA

first eukaryotic common ancestor

LECA

last eukaryotic common ancestor

Metazoans

Multicellular animals that possess more than one kind of cell and have their cells organized into tissues and organs (poriferan, cnidarian and bilaterian)

Poriferans (Sponges)

No symmetry, simplest body plan, Single tissue layer, An accumulation of cells designed to pump and filter water for nutrients

Cnidarians

Double tissue layer, no through gut. If tentacles up they are a polyp, if down they are a medusa

Bilaterians

Three tissue layers, Includes a through gut, Includes almost all animals, except poriferans and cnidarians

Resolving Darwin’s Dilemma

Can use three diff categories of evidence for how complex life in Cambrian appeared (Precambrian fossils, Biomarkers, Molecular Clocks)

Precambrian Fossils

Eukaryotic fossils in Ediacarin, Organisms lack mineralized skeletal remains, so they are rare. Preservation requires a unique set of circumstances only present in the Precambrian

Algal Mat Preservation

Fossil was preserved in a bacterial mat that encased it when it died, and allowed for soft tissue to be preserved.

Doushantou Formation

Known for fossilized embryos and sponge spicules, 635 - 551 Ma

Mistaken Point

Known for deep sea animals like Charniodiscus and Fractofusus, 565 Ma

Ediacara Biota

Ediacara Hills, Australia (635-542 Ma), Known for diverse assemblage of (mostly) soft bodied organisms, preservation via bacterial mats, Tons of “firsts” like first bilaterians, mobility, burrowing, sexual reproduction

Biomarkers

Fossilized organic molecules only created by certain organisms, can be used as evidence for organism during time. Biomarkers for sponges exist from 650 Ma, just after the Cryogenian

Molecular Clocks

Genetic method where you compare DNA of two modern organisms to back calculate how long ago they diverged from each other. Date origin of Eukaryotes to when sponge biomarkers occur, Confirmed!

Precambrian and Cambrian Boundary

defined by the trace fossil T. pedum, evidence of complex burrowing behavior and marks a major ecological innovation

Burrowing

Occurs in any seafloor that isnt anoxic, well recorded in fossil record, good for protection, predation/ambush, reproduction, feeding

Burrowing Ecosystem Changes

Increased nutrient and gas exchange at the sediment/water interface, Hindered bacterial mat growth, Hindered preservation of soft-bodied Ediacaran organisms

Paleozoic Continents

Laurentia, Baltica, Siberia, China, Gondwana

Laurentia

mainly North America, also including some of Greenland, northwestern Ireland, Scotland

Baltica

Russia (west of the Urals) and most of northern Europe

Siberia

Russia (east of the Urals) and north Mongolia

China

northern China, Indochina, and the Malay Peninsula

Gondwana

supercontinent composed of South America, Africa, India, Australia and Antarctica

Wilson Cycle

every ~500 million years a supercontinent will break apart and form into another one

Cratonic Sequences

large-scale, craton-wide sedimentary rock units deposited during sea-level rise and fall, bounded by major unconformities

Causes of Cratonic Sequences

Global climate (ice sheet growth and collapse), Global tectonics (sea floor spreading or basin expansion)

Laurentia Ordovoian

Great preservation of shallow marine rocks across the continent; rich fossil record preserved in Cincinnati Arch region and Great Basin region

Taconic Orogeny

major mountain-building event resulting from island arcs converging along (modern) East coast, first collision that formed Appalachians

End-Ordovician Climate

Gondwana migrated over the south pole causing cooling event which is probably cause of end ordovician mass extinction

Laurentia Silurian

Recovery from end-Ordovician climate change and mass extinction, more land exposed and shallower oceans

Laurentia Devonian

Many small epicontinental basins that experienced anoxia, resulting in several small/regional extinction events that together form the Late Devonian Mass Extinction

Acadian Orogeny

major mountain-building event resulting from Baltica and Avalonia microcontinents colliding with east margin of Laurentia, second collision that formed Appalachians

Devonian black shales

formed during anoxic events, are found globally throughout the Devonian, contain cool fossils when O2 whifts happened

Laurentia Carboniferous

Marine regression produced craton wide unconformity, only in Laurentia - differentiates Carboniferous into Mississippian and Pennsylvanian

Alleghenian Orogeny

Biggest mountain building event caused by Gondwana crashing into Laurentia, third and final Appalachian building event

Laurentia Permian

Ongoing continental collision between Gondwana and Laurentia, Very little epicontinental sea on Laurentia through this time period, Pangea is assembled

Cambrian Explosion

The sudden appearance of complex animals with mineralized skeleton remains in the fossil record, 542Ma, All major phyla (& body plans) appear by end of event

Burgess Shale

Middle Cambrian fossil deposit in BC that preserves many soft-bodied organisms from the Cambrian Explosion, contained many animals never seen before

Burgess Shale Type (BST) Preservation

preserves soft-bodied organisms as thin, flattened carbonaceous films in fine-grained marine mudstones

BST Requirements

Early inhibition of microbial activity in anoxic sediment, Global ocean geochemistry with low sulfate concentrations and low-oxygen bottom waters to reduce oxidation

Qingjiang Fossils

BST fossil site from early Cambrian with over 53% of its identified species being new to science

Background Extinction

the normal rate at which individual species go extinct

Mass Extinction

a period of time with numerous species extinctions, significantly greater than the normal background rates

Pull of the Recent

Trend of increasing diversity over time

1st Big Mass Extinction

Ordovician, Rapid global climate change

2nd Big Mass Extinction

Devonian, Marine anoxia caused primarily by paleogeography

3rd Big Mass Extinction

Permo-Triassic, Siberian traps (LIP) caused global warming, ocean acidification, ocean anoxia, volcanic darkness, photosynthesis shutdown, toxic metal poisoning

Large Igneous Provinces (LIPs)

massive, planetary-scale accumulations of igneous rock formed by colossal, rapid bursts of volcanism that dramatically alter Earth's environment

4th Big Mass Extinction

Triassic, Central Atlantic Magmatic Province (LIP) caused global warming, ocean acidification, toxic metal poisoning

5th Big Mass Extinction

Cretatious, Chicxulub meteorite impact