changing climate

Question 1

how is coal lithological evidence for climate change?

Answer 1

forms in an area of high rainfall and temperatures e.g. tropical rainforests found in equatorial regions

Question 2

how is desert sandstone lithological evidence for climate change?

Answer 2

Dune-forming latitudes are generally around 20-30 north and south of the equator

Question 3

how are evaporites lithological evidence for climate change?

Answer 3

form when rain fall is low and evaporation is high e.g. hot deserts. latitudes 20-30 north and south of equator.

Question 4

how are tillites lithological evidence for climate change?

Answer 4

form at high altitudes >60 north or south of the equator. there are glacial deposits in low latitudes as small areas of high altitude glaciers

Question 5

how are reef limestone lithological evidence for climate change?

Answer 5

built mainly of colonial coral restricted to latitudes of less than 30 north or south of the equator

Question 6

how are corals palaeontological evidence for climate change?

Answer 6

only thrive where they can successfully exploit symbiotic relationship with algae. restricted to 30 north and south of the equator

Question 7

how are plants palaeontological evidence for climate change?

Answer 7

tree rings, leaf size and shape are good climate indicators

Question 8

why is there more O18 in the oceans during colder periods?

Answer 8

in periods of glaciation O16 is trapped in glaciers causing the ratio of O16 and O18 to change

Question 9

what evidence is there for changes in oxygen isotopes in the oceans?

Answer 9

there are changes in the oxygen incorporated into calcium carbonate shells.

Question 10

under normal circumstances what happens to the O16 in the oceans?

Answer 10

lighter O16 is removed easily by evaporation so leaves more O18 in the oceans. The O16 in the evaporated water is returned to the ocean after falling as rain or snow and running off back through the river system.

Question 11

which carbon isotope do plants preferentially take up?

Answer 11

12C

Question 12

Why are carbon isotopes more useful than oxygen isotopes?

Answer 12

they are more resistant to diagenetic change

Question 13

what happened to the 13C ratios in the ocean during glaciation?

Answer 13

during glaciation, terrestrial biomass was greatly reduced, so plants took up less 12C. Therefor the oceans appeared to be depleted in 13C.