April 1st lecture

Question 1

What are ocean sediments?

Answer 1

They are the accumulation of innumerable solid particles of many different types of materials that are deposited on the seafloor, by a process called sedimentation

Question 2

True/False;

Sediments cover the whole worlds oceans?

Answer 2

false:
They almost cover the whole worlds oceans,
Although they do not cover areas where there is fast currents as they get swept away.

Question 3

What is the size range of the sedimentary particles?

Answer 3

0.001mm to 10cm

Question 4

Does the law of superposition apply to sediments?

Answer 4

Yes, oldest on the top and youngest on the bottom

Question 5

Why is it important to apply the law of superposition to the analysis of sediments?

Answer 5

Because it allows us to study what has happened in the past by looking at the preserved deeper levels of sediment.

Question 6

How can we use sediments to examine what the climate was like in the past?

Answer 6

Differences in sediment structure, content,

deposition rate can all tell us about past climates

Question 7

What is one assumption that we make when we examine sediments?

Answer 7

We assume that the sediments are unchanged over time

Question 8

What is one key factor that we must look for when examining sedimentary records? ( tells about relative life during that period )

Answer 8

• considering fossils preserved in
  the sediments
• the temperature range that a species exists in at present may give a temperature range for the water at the time of the fossils death.

Question 9

What are Oxygen Isotope Studies?

Answer 9

It is the study of the ratio of O16 /O18

Question 10

What isotope of oxygen is water vapor rich in? what is left in the ocean?

Answer 10

Since lighter water is easier to evaporate than

heavier water, water vapour is enriched in O16

Question 11

What happens to the concentration of oxygen isotopes when the earth cools?

Answer 11

Water vapor condenses as show and then ice into the polar ice caps, rather than being returned into the ocean.

Thus, O16 is transferred to the glacier (meaning there is less of it in the oceans) and thus the oceanic ratio of O16 /O18 gets smaller.

Question 12

How can we use oxygen isotopes/sediments to determine temperature in the past?

Answer 12

by examining the different oxygen isotopes in them.

When its warmer there is more O16 in the ocean, rising the 018 / 016 ratio

When its colder the ratio is smaller as there is less O16 in the ocean

Question 13

How do we measure the oxygen isotope concentrations? ( two ways )

Answer 13

-Gas bubbles in ice cores taken from glaciers can show the atmospheric composition of each isotope at the time
the air was trapped

• When the organisms die, their shell material falls to the seafloor and is incorporated into the sediments these sea creatures incorporate the isotopes into their shells. By examining the isotopic changes in cores recovered from the sediments, we
  can examine past climate changes

Question 14

How has earths climate varied over the last
1000 years
10,000 years
2-3 Ma

Answer 14

– ~0.5°C over the last 1000 years
– 2-3°C over the last 10,000 years
– 10°C over the last 2-3 million years

Question 15

What are periods of large cooling known as?

Answer 15

ice ages, where polar ice caps extent to much lower latitudes.

Question 16

When the climate cools what happens to the oceans?

Answer 16

• the oceans cool and contract

- polar ice sheets expand as water is transferred to the land as snow

Question 17

What happens to the oceans when the climate heats up?

Answer 17

The oceans expand as the heating melts ice and snow, which then flows to teh ocean, raising sea levels.

Question 18

What is Eustatic sea level change

Answer 18

When oceans expand due to rising climate and melting Ice, and when the oceans retract due to cooler climate and build up of ice and snow on land.

These changes occur throughout the world.

Question 19

What is Isostatic sea level change?

Answer 19

When the weight of overlaying ice sheets press down on the continental crust underneath it.

Question 20

How can ice push down on the earths crust?

Answer 20

The continents float on the Earth’s Asthenosphere
– a fluid level below the earth’s crust, such that adding more weight causes the object to be pressed down, as if weight is added to a log floating in water

Question 21

How long does it take for isostatic sea level change to take place?

how far is Antarctica pushed down by its ice?

Answer 21

It can take millions of years

Antartic is pushed down by 400m

Question 22

Is isostatic sea level change global or localized?

Answer 22

It is localized to the content in question

Question 23

Is north america rising or falling from the last ice age?

Answer 23

slowly rising

Question 24

What is Steric sea level change?

Answer 24

The change in sea levels due to alteration of the oceans density

Question 25

How does Steric sea level change occur?

Answer 25

Warming leads to a decrease in density
– With a constant mass, a density decrease leads to a volume
increase. Thus steric sea levels rise in the change in sea level due to changes in ocean volume (from temperature changes)

Question 26

Does Steric sea level change affect the whole ocean? and all temperatures?

Answer 26

This steric sea level rise occurs at all ocean temperatures and is one of
the major contributors to sea level changes during the 20th and 21st
centuries

Question 27

What happens in Steric sea level change when the ocean temperature is high?

Answer 27

Water at higher temperature or under greater pressure (i.e., at greater depth) expands more for a given heat input, so the global average expansion is affected by the distribution of heat within the
ocean.

Question 28

How does salinity affect Steric sea level change?

Answer 28

Salinity chances within the ocean has a significant impact on the local density and this the local sea level , but has little effect on global avarge sea level, more localized.