Lecture 5 - Climate fluctuations of Earth’s history

Question 1

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

Answer 1

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

Question 2

What happens to deep sea cores overtime?

Answer 2

They’re destroyed via subduction

Question 3

What are turbidite deposits?

Answer 3

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

Question 4

What principle does turbidite deposition ignore?

Answer 4

Principle of superposition

Question 5

What type of grading does turbidite deposition result in?

Answer 5

Graded bedding

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Evolution and extinction of life forms that have no living equivalents

Question 9

What % of species that have ever lived are extinct?

Answer 9

99.9%

Question 10

What is the average lifespan of a species?

Answer 10

1-10 million years

Question 11

What two states has climate fluctuated between?

Answer 11

Global cooling - Ice house

Global warming - greenhouse

Question 12

What is the glacial features during global cooling?

Answer 12

Glaciers at high latitudes and possibly globe wide

Question 13

What is the glacial features during global warming?

Answer 13

Earth is ice free

Question 14

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

Answer 14

We experience everything between the two polars

Question 15

When is the Cenozoic ice age?

Answer 15

Last 30 Ma

Question 16

When was the Permo-Carboniferous Ice Age?

Answer 16

290 Ma

Question 17

When was the Ordovician Ice Age?

Answer 17

440 Ma

Question 18

When were the Precambrian Ice Ages?

Answer 18

> 570 Ma

Question 19

How many Precambrian Ice Ages have there been?

Answer 19

Three

Question 20

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

Answer 20

The entire globe

Question 21

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

Answer 21

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

Question 22

Why are records from the precambrian era poor?

Answer 22

Not many have been preserved on land due to erosion

In the ocean they have been subducted

Question 23

When did glaciations occur in the Pre-cambrian era?

Answer 23

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)

Question 24

What triggered the snowball earth theory (and slushball)

Answer 24

The 700-650 Ma ice age

Question 25

What is the hypothesis of the Snowball Earth theory?

Answer 25

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

Question 26

What is evidence for the Snowball Earth theory?

Answer 26

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

Question 27

What is glacial striae?

Answer 27

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

Question 28

What is glacial tillite?

Answer 28

Unsorted, seemingly random glacial deposits when it melts/breaks

Question 29

What is drop sediment?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

How could life survive a snowball earth?

Answer 31

Hot springs? Deep sea vents? Volcano-heated ponds? | Or - a slushball earth, where the equator had open areas where life survived

Question 32

When was the Ordovician Ice Age?

Answer 32

440 Ma

Question 33

What did Gondwanaland do in the Ordovician ice age?

Answer 33

Crossed the South Pole

Question 34

What continents made up Gondwanaland?

Answer 34

S America, Africa, Antarctica, Australia and India

Question 35

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

Answer 35

bedrock was scratched by glaciers and glacial deposits were laid down

Question 36

When was the Permo-Carboniferous Ice Age?

Answer 36

290 Ma

Question 37

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

Answer 37

Antarctica, Africa, South America, India, Australia

Question 38

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

Answer 38

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

Question 39

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

Answer 39

On the equator

Question 40

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

Answer 40

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.

Question 41

When was the Cenozoic ice age?

Answer 41

30 Ma to now

Question 42

Where was glaciation during the Cenozoic ice age?

Answer 42

In high latitudes

Question 43

What happens during glacial periods?

Answer 43

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

Question 44

What happens during interglacial periods

Answer 44

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

Question 45

When was the last glacial period?

Answer 45

Devensian Ice age - peaked from 21-18 Ka

Question 46

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

Answer 46

climate cooled leading to deforestation | evidence: pollen record

Question 47

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

Answer 47

the water gets locked up on the continent as ice

Question 48

What was sea level like in the Devensian ice Age?

Answer 48

150m lower than it is today

Question 49

What is CO2 like in the Holocene?

Answer 49

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