GLG exam 3

Glacier--mass of ice formed on land from snow that survives from year to year and creeps down slope or outward due to the stress of its own weight (recrystallization / compression)

Form + Mvmnt-- due to gravity . top is fracturing, middle is deformed and compressed like warped plastic, sliding (basal slip) occurs at base. can flow few cm / yr or few meters/ day

• Alpine glaciers: form on mountains and flow down valleys

• Continental glaciers: form at higher latitudes and flow to lower latitudes

Moraines-- landforms made of Till (the unsorted, unlayered sediment deposited directly by glacial ice; can be fine as clay or large as boulders)

• lateral and medial moraines: linear strips formed along edge of alpine glacier

• end moraine: curved, elongated ridge that accumulates at the “downstream” end of glacier

  • terminal moraine: marks glacier’s farthest advance

  • recessional moraine: a lateral or end moraine formed during a pause in a glacier’s retreat

• ground moraine: till that is deposited along the base of a glacier

Erratics “imported rocks”

Till, including moraines

Depression of the land

Scouring (striations + grooves)

Lowering of sea level

Migrations of species

Evidence of past

• long island, martha’s vineyard, cape cod, nantucket island were formed from end moraines

External causes:

1. solar output variations (10% birghter?) appear to be too small and short-lived at present, but may have been larger in the past or may be larger than we think

2. Milankovitch cycles (orbital fluctuations): separate cycles on different time scales, but periodically experience collective reinforcements that are enough to cause global climate change

   1. eccentricity: ellipticity of earth’s orbital path -- 100,000 year cycle

   2. obliquity: degree of tilt of earth’s rotational axis -- 41,000 year cycle

   3. precession: wobble of Earth’s rotational axis over time -- 26,000 year cycle

Internal factors:

1. The Albedo Effect: the percentage of solar radiation that is reflected back into space changes the amount of energy available to heat the planet

2. The Greenhouse Effect: gases effective in absorbing long-wave (infrared) radiation effectively strengthen the effect of solar radiation

3. Plate tectonics: changes in geography influence activity of ocean currents, atmospheric co2 levels, distribution of heat, present or absence of lands at poles, etc.

(2 other internal: volcanic activity and changes in biogeochemical cycles)

factors of Pleistocene glaciation include tectonics and ocean circulation

• closure of Tethys Sea (Oligocene) limited warm water flow . placement over South Pole established Antarctic circumpolar current. Uplift of Himalayas lowered atmospheric co2. Together, these events led to Antarctic ice sheets, which accelerated formation of oceanic waters.

• after some time, formation of Isthmus altered NA circulation and glaciation had begun

The division between Pleistocene and Holocene falsely implies that the “ice age” is over (no, but, interglacial?)

This ice age has been going on for 2.6 million years. Ice sheets have expanded and melted at least 17 times in the last 2 million years.

oxygen isotope data correlates to temperature

oxygen isotope compositions of shells of planktonic forams provide global temperature information

isotopic mass fractionation , the back and forth between heavier, warmer temp isotopes (o18) and lighter, cooler isotopes (o16) , preserve a record within glacial ice of the fluctuating global temperatures over time.

• trapped air bubbles in glacier ice also show paleoatmospheric composition (greenhouse gas concentrations!), as well as a bunch of other environmental data (like volcanic history for example)

eccentricity + obliquity (tilt) + wobble = glaciation fluctuation

by combining the above aspects of Milankovitch cycles, we get a plot of “solar radiation received” that matches very well with global temperature fluctuations indicated by ice core oxygen isotope data.

-- geologists are somewhat unsure why this happens, but the evidence is clear that it does

Terrestrial mammal fauna of NA were much larger than their modern counterparts

Herbivores: elephants (mammoth, mastodon), beaver size of bear, camel (20% larger), bison w 7ft horns, 1 T weighted armadillos, 3T weighted ground sloths

Carnivores: larger bears, dire wolf (30% heavier), lions (1.5x as heavy)

Teratorns: large flying predatory birds

TERATORN (Argentavis)-- wingspan of 24 ft

related to storks, modern turkey vultures, and condors

weathering of Himalayas caused decrease in atmospheric CO2 levels, which results in lower temperatures and changed precipitation patterns

(don’t know answer to second question. weathering?)

‘The Great American Schism’ was the joining of N. American and S. America 3-5 Ma when the Isthmus of Panama arose as an island arc.

S → N : monkeys, anteaters, armadillos, porcupines, opossums, sloths, etc.

N → S: camels, pigs, deer, horses, elephants, tapirs, rhinos, rats, skunks, squirrels, bears, dogs, raccoons, cats, etc.

• more animals went southward than northward because NA had fewer tropical habitats by Pliocene time.

• marine species in Caribbeans and Pacific began to evolve differently from one another: speciation + extinction

Climate Effects:

• Caribbean waters became warmer, saltier, stable.

• Gulf Stream delivers warmer water to North Atlantic

• Pacific waters became cooler and more nutrient rich

Asia → Africa Invasion of the “Mongol Hordes”

• Suids

• Giraffids

• Rhinos

• Bovids

• Fissiped carnivores (toes separated at base like dog)

Shift toward increasingly drier and cooler climate in Miocene led to evolution of C4 grasses

Compared to C3 photosynthesis, C4 is more efficient in drought conditions, high temperatures, or CO2 shortages

C4 plants are less selective about needed carbon-12 isotope; over time carbon-13 was more prominent

Because C4 grasses have sharper phytoliths, grazers who evolved high crowned teeth rose in dominance (browsers decline)

in addition, flowering herbs rose in plant dominance.

The combination of grasses and herbs resulted in diversification of smaller rodents and songbirds with corresponding diets. → snake diversify

Mammals evolve

Herbivores (Artiodactyls like deer and bovid & elephants) & Omnivores (giraffes and pigs)

Carnivores (families of dog, cat, bears, hyena) benefitted from herbivore expansions

diatoms underwent tremendous diversification (maybe driven by C4 grasses)

corals, and other warmer water taxa, became restricted to lower latitudes due to cooling

whales radiate and diversify

• Toothed whales : predators - first

• Baleen whales: “filter feeders” - evolved later from toothed whales

Cause: calcareous (coccolithophores + foraminifera) and siliceous (radiolarians) oozes and red clay on the ocean floor established due to vigorous deep ocean circulation, upwelling of cold nutrient-rich waters, and deepening of calcite compensation depth

[Cascading radiation & diversification)

The evolution of grasses and herbaceous plants required the help of small animals to distribute seeds.

The diversification of these small rodents (mice, rats) and songbirds corresponded with grass/herb/seed diets.

In turn, snake predators diversified to pursue rodents into their burrows and to climb trees to reach songbirds eggs/chicks

Features:

Large eyes, turned forward for effective steroscopic vision

grasping hands and feet allow primate to forage alone narrow branches

nails instead of claws

primate fetuses have rapid brain growth rates so theyre born with larger brains than other mammals

gestation time is long for body size, and primates have small litters of young that develop slowly and for a long time

primates have evolved high learning capacity, complex social interactions, and unusual curiosity

Origin of Primates

85 million years ago in the tropics

most closely related to dermopterans, “flying lemurs”

2 primate groups == Prosimians “wet nose” + Anthropoids “dry nose”

Prosimians: small-brained, small-bodied

• Lorises (nocturnal insect hunters living in tropical forests of india, sri lanka, south asia) + Pottos (nocturnal tree-dwelling omnivores of tropical africa -- short fingers)

• Lemurs: fossil record to Miocene. confined to madagascar

Anthropoids: relatively large-bodied and large-brained monkey and apes.

1. ceropithecoids (old world monkey): macaque, baboon, mandrills, colobus

2. Ceboids (new world monkey): monkey type-- spider, howler, emperor, tamarin

3. hominoids: gibbons, apes, humans - longer arms + no tail . swing underneath branches

hylobatids (gibbons), pongids or asian apes (orangutans), african apes (chimps + gorillas), and hominins (humans)

certainly evolved from Aegyptopithecus , an African anthropoid genus

Humans made split from common ancestor around 7 Ma

The hominoid Gigantopithicus went extinct at the beginning of the Pleistocene’s last ice age in tropical forests of modern day China-- changed climate made its size a fatal handicap

Features of Homo sapiens (in chronological order) : small canines, thick enamel, bipedalism, big brains, tool-making, meat-eating, big bodies

DNA evidence shows there was interbreeding between Homo sapiens and Neanderthals (Homo neanderthalensis)

• 2.5% of average non-African human’s genome is made of Neanderthal DNA; 0% in modern Africans

Fossils of Ardipithecus, found in Middle Awash, Ethiopia (2009), show adaptations that combine tree-climbing AND bipedal activity

• Ardi (ground) pithecus (ape) ramidus (root) = “root of all ground apes”

Dr. William K. Hart chemically analyzed and correlated the ash layers associated with fossils to ash layers dateable by the Ar/Ar method. Found that Ardi fossils ~4.42 Ma old

East African Rift Valley -- over 30 million years of episodic bimodal (basalt-rhyolite/trachyte) continental rift volcanism AND extensional tectonism (uplift and subsidence) and sedimentation

• [[ find out why its a good site]]

The transition from woodlands → savannas did not drive bipedal evolution

• Ar. ramidus fossils showed wooded environment -- forest-to-woodland based diet

Bipedalism evolved before large brains

Climate of paleocene-eocene: Very warm (like cretaceous) and experienced 10,000 year long thermal maximum -- temperature spike <-- high co2 <-- Pangea breakup

Terrestrial plants: Angiosperms spread over land, Ferns dominated with heat spike (fern spike), palms and cycads to 60N - temperate plants N of Arctic cicrcle

Terrestrial animals: archaic raca explosive diversification early on

Coccolithophorids survive K-Pg event, but never recover their former diversity

Nummulitids: 1in disc-shaped forams become important limestone builders in shallow seaways (pyramids)

Hexacoral, took until late eocene bc mg2+/ca2+ ratio was too low

Echnoids continue their dominance of echinoderm fauna, sand dollars evolve

Giant predatory sharks replace marine reptile

Origin of whales, manatees and sea cows, desmostylians, seals, and sea lions

PETM: Paleocene-Eocene Thermal Maximum

Heat spike : 4-5 C increase; 3-4x co2 increase

Possible causes: Positive feedback loop of methane gas release

release, reduced burial of C, Iceland Hotspot triggering volcanism (initial catalyst)

Increased pCO2 on marine life, insects, and plants:

• marine life: warming caused o2 depletion, dissolution of calcium carbonates (caco3) / 70% extinction of benthic (bottom dwelling) forums; shallow were fine

• Insects: CO2 does not directly affect insects (but developmental decrease occurs since foods (plants) nutritional content had decreased)

• Plants: Growth rates increased and nutrient content of plants decreased

Relevant to modern climate because PETM provides best known analog for understanding impacts of modern-day global warming and massive carbon input to ocean + atmosphere

Initiation of Antarctic circumpolar current due to separation of Antarctic and Australia isolated Antarctic from warm-water currents and caused continuous circular water flow which reduced deflection toward lower latitudes -- allowed right amount of moisture for glacier building

Cooler, drier climates changed the course of terrestrial evolution

• forests heavily reduced, leaving grasslands and savannas.

• Lost habitat and food sources for forest-dwellers, loss of cover for ambush-style predators -→ out competed by running carnivores

• Toed hooves left, morphed one for faster running

• Continuous tooth growth

Pre-Paleogene grasses could not tolerate continual grazing, so they occupied moist swampy areas

Advent continuous growth allowed later grasses to grow back quickly after grazing, allowing grasses to spread and forests shrank in dry conditions of Oligocene

Phytoliths: Silica structures in grass makes chewing it like sandpaper, it grinds teeth down over time. Grazers adapted with high-crowned teeth for continuous tooth growth. When tooth eroded, more would be pushed out.

* grassland expansion was very important to evolutionary changes in mammals

Late-cretaceous Laramide orogeny: Subhorizontal subduction brings volcanism (high -→ angle change) to Colorado, Wyoming, new Mexico

Formed Unita and Green River Basins

Unique because the Badlands of South Dakota, which consist of sediments eroded from Rocky Mts, contain a very valuable fossil record of Early Cenozoic mammal and plant evolution.

Cenozoic Era - Quaternary Period - Holocene Epoch

The Younger Dryas, “the big freeze”: a cold (and dry) interval between 12.8 ka and 11.7 ka, followed by rapid warming which interrupted thermohaline circulation

• linked to humans first adoption of agriculture in Middle East

chain of events:

1. (12.8 ka) warming-induced flux of water to Atlantic or Arctic Ocean due to collapse of N. American ice sheets, which deflected northward flow of warm saline from south → rapid cooling and drying of northern latitudes

2. cooling persists until fresh water ‘lid’ is removed form N. Atlantic Ocean

3. (11.7 ka) ends with rapid warming of 7C in 3 years, resulting in rapid positive feedback

Holocene Climate Optimum: Warm and wet climate (post Younger Dryas) caused favorable conditions for human agriculture in Middle East “Fertile Crescent”, then in Egypt, Mesopotamia, etc., and finally to Europe

Transition into Neoglacial, cool and dry climate which brought severe droughts and famine → creating a need for complex governments. sudden and severe drought led to “Dark Ages”

• possible catalyst for barbarian migrations leading to fall of Roman Empire

Medieval Warm Period 950-1250 CE was 1C warmer than today (oof) causing max. solar output, deforestation of Europe, low volcanic activity, stronger Gulf Stream [weirdly tho, global temp avg. was lower] → Norse Vikings + Europeans flourish, Mayan civilizations collapse from drought.

The Little Ice Age: N. Hemisphere Event: cooler/wetter post-MidE-warm p. caused European famines in 14th-15th century, leading to the downfall of N. African and Indian civilizations, famines/floods in china

1815 Eruption of Mt. Tambora (Indonesia) was the largest volcanic eruption in history -- ash fell 810 miles from site. Led to the “Year Without a Summer” in 1816, global temp dropped up to 1.4F

• agricultural disaster in N. Hemisphere-- greatest subsidence crisis in Western world

• New England (below freezing, sow, frost, and river ice through summer months), failed harvests in Europe, disrupted monsoon season in Asia

  → human adaptations: bicycle (no horses), Frankenstein, settlers move to midwest, invention of mineral fertilizers

Glacial maxima of Holocene epoch show sea level falling 330-450 ft, causing land bridges (allowing animals to cross), increased fluvial downcutting (fjords + terraces), and acceleration of sediment delivery to the ocean, with sand often bypassing the continental shelves

• important to note that if glaciers melted, sea level would rise 210ft, drowning 15% of land area + higher temp expands water volume

simple extrapolation of current climate trends is unhelpful since tipping points are reached which may cause rapid positive feed back loops:

• loss of Arctic sea ice will result is region warming instead of ice melting in summer heat

• evergreens replacing tundra changes albedo in northward and in Greeland.

  • progressive release of methane (23x worse than co2)

Its been proposed that the “Anthropocene Epoch” be validified as a geologic time of humans disrupting climate and ecosystems but, because its generally short and unsustainable, the Anthropocene would be better categorized as an event.

If adopted, possible start times are: Industrial Revolution, Neolith (deforestation/ agriculture), 1st atomic bomb detonation

We expect a diversity of minerals on a planet remain at low established value until life evolves because we know that the mineralogy of terrestrial planets and moons evolves as a consequence of selective physical, chemical, and biological processes.

Stage 7: “The Great Oxidation Event”

• rise of oxygenic photosynthesis and rise of an oxygen-rich atmosphere (2.5 - 1.9 Ga):

• more than 2500 minerals are hydrated oxidized weathering products of other minerals

Stage 10: biologically-induced weathering and biomineralization as life dominates and diversifies

• invertebrate and vertebrate animals begin to use carbonate, phosphate, and silica through new mechanisms of mineralization (0.542 Ga - present)

• rise of land plants about 400Ma led to rapid soil production and an order of magnitude increase in the rate of clay mineral production

By looking whether the following processes are acting at or near a planet’s surface will determine its degree of mineral evolution, and therefore, its closeness to life

• progressive separation + concentration of elements from their OG distribution in the presolar nebula

• activity involving pressure, temperature, H20, CO2, and O2

• the production of thermodynamically metastable minerals and mineral-forming reactions that could not occur abiotically