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LEC.103 > Lecture 5 - Climate fluctuations of Earth’s history > Flashcards

Lecture 5 - Climate fluctuations of Earth’s history Flashcards

1
Q

Which is normally more complete - rock cores on land or in the sea and why?

A

Rock cores on land are typically much less complete than deep sea cores (more erosion of land)

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2
Q

What happens to deep sea cores overtime?

A

They’re destroyed via subduction

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3
Q

What are turbidite deposits?

A

when material doesn’t stay on the ocean shelf, and is disrupted, so the densest material settles first, and is overlaid by finer sediment

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4
Q

What principle does turbidite deposition ignore?

A

Principle of superposition

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5
Q

What type of grading does turbidite deposition result in?

A

Graded bedding

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6
Q

Why do we need to drill in multiple locations in an area?

A

if you drill in one place, you don’t get a complete record

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7
Q

What is the general relationship between time and completion of rock records

A

the further we go back in time, the less complete the rock records we find are

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8
Q

Why do fossil records become harder to interpret as they get older?

A

Evolution and extinction of life forms that have no living equivalents

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9
Q

What % of species that have ever lived are extinct?

A

99.9%

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10
Q

What is the average lifespan of a species?

A

1-10 million years

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11
Q

What two states has climate fluctuated between?

A

Global cooling - Ice house

Global warming - greenhouse

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12
Q

What is the glacial features during global cooling?

A

Glaciers at high latitudes and possibly globe wide

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13
Q

What is the glacial features during global warming?

A

Earth is ice free

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14
Q

What happens in the transformative period of Earth’s climate?

A

We experience everything between the two polars

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15
Q

When is the Cenozoic ice age?

A

Last 30 Ma

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16
Q

When was the Permo-Carboniferous Ice Age?

A

290 Ma

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17
Q

When was the Ordovician Ice Age?

A

440 Ma

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18
Q

When were the Precambrian Ice Ages?

A

> 570 Ma

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19
Q

How many Precambrian Ice Ages have there been?

A

Three

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20
Q

How much of the globe do we believe the Pre-Cambrian ice ages covered?

A

The entire globe

21
Q

How much of the earth do younger ice ages appear to cover?

A

only the southern hemisphere, or southern and northern, but not the entire world

22
Q

Why are records from the precambrian era poor?

A

Not many have been preserved on land due to erosion

In the ocean they have been subducted

23
Q

When did glaciations occur in the Pre-cambrian era?

A

2700-2300 Ma - Evidence from Canada, N Europe, S Africa
950 Ma - Evidence from Greenland, Scandinavia, Africa, Australia, E Asia
700-650 Ma - Glacial deposits on all continents (Earth may have been completely covered by ice)

24
Q

What triggered the snowball earth theory (and slushball)

A

The 700-650 Ma ice age

25
Q

What is the hypothesis of the Snowball Earth theory?

A

Earth’s ocean and land surfaces covered by ice from poles to equator, at 2.4 billion and 580 Ma

26
Q

What is evidence for the Snowball Earth theory?

A

Rocks of the age which were near the equator at these times, have evidence of glacial deposition: e.g. Tillitie, glacial striae

27
Q

What is glacial striae?

A

Rocks in the bottom of glaciers scraping rocks that it passes over

28
Q

What is glacial tillite?

A

Unsorted, seemingly random glacial deposits when it melts/breaks

29
Q

What is drop sediment?

A

large rocks on the ocean bed where the glacier melted and released it’s sediment (the oceanic glacial tillite equivalent)

30
Q

How could the Earth come out of icehouse conditions while in permafrost?

A

Volcanic eruptions? Increase greenhouse effect
Decreased CO2 sinks: aka decrease in weathering and CO2 drawdown?
Decrease photosynthesis?

31
Q

How could life survive a snowball earth?

A

Hot springs? Deep sea vents? Volcano-heated ponds?

Or - a slushball earth, where the equator had open areas where life survived

32
Q

When was the Ordovician Ice Age?

A

440 Ma

33
Q

What did Gondwanaland do in the Ordovician ice age?

A

Crossed the South Pole

34
Q

What continents made up Gondwanaland?

A

S America, Africa, Antarctica, Australia and India

35
Q

What proof is there that the Sahara crossed the South Pole?

A

bedrock was scratched by glaciers and glacial deposits were laid down

36
Q

When was the Permo-Carboniferous Ice Age?

A

290 Ma

37
Q

Where is glacial evidence of the Permo-Coniferous Ice Age?

A

Antarctica, Africa, South America, India, Australia

38
Q

What was the effect of the Permo-Coniferous Ice Age on the UK?

A

no glacial deposits, but tropical rainforest growth contributed to massive coal accumulations

39
Q

Where was the UK during the permo-carboniferous Ice Age?

A

On the equator

40
Q

What is evidence that the Earth was partially covered by ice during Ordovician and Permo-Carboniferous glaciations?

A

The continents with evidence of ice cover (e.g. Australia, Africa etc) have moved from their current positions (plate tectonics and continental drift).
If full cover, why were regions such as the UK, warm?
Glacial striations indicate ice movement out from a central region.

41
Q

When was the Cenozoic ice age?

A

30 Ma to now

42
Q

Where was glaciation during the Cenozoic ice age?

A

In high latitudes

43
Q

What happens during glacial periods?

A

Expansion of glaciers
Erosion of underlying rock
Glacial transport of sediment great distances
Global sea level lowered

44
Q

What happens during interglacial periods

A

Retreat of glaciers
Deposition of till/boulder clay/glacial deposits
Screes developed and soils established
Global sea level raised

45
Q

When was the last glacial period?

A

Devensian Ice age - peaked from 21-18 Ka

46
Q

What happened after the Devensian Ice Age(and evidence for this)?

A

climate cooled leading to deforestation

evidence: pollen record

47
Q

What happens to the hydrosphere and cryosphere when we go into a glacial period?

A

the water gets locked up on the continent as ice

48
Q

What was sea level like in the Devensian ice Age?

A

150m lower than it is today

49
Q

What is CO2 like in the Holocene?

A

huge spike in atmospheric CO2 in recent time, due to human activity.

LEC.103 (5 decks)

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