Past Cliamtes

Question 1

Which cycle provides a framework to understand long-term changes recorded in the rock record?

Answer 1

The J.Tuzo Wilson Cycle

Question 2

Which aspects can the Wilson Cycle help us to understand?

Answer 2

-Global Climate
-Composition of the Atmosphere
-Sea-level changes
-Past and Present Distribution of Continents

Question 3

What are examples of Climate Change indicators?

Answer 3

-Lithological evidence = sedimentary sequences provide evidence of palaeoenvironments and climatic zones - red sandstone evaporates (hot desert), coal (tropical), limestone (greenhouse deposits), tillites (icehouse deposits)
-Palaeontological evidence = fossil land plants (leaves/pollen) - evidence of a range of climatic regimes and corals (warm seas)
-Geochemical evidence = 18O/16O isotope ratios in fossil shells

Question 4

Explain the relative importance of oxygen isotope ratios when evaluating past climates.

Answer 4

-Oxygen isotope ratios in fossil shells indicate the temp of ancient ocean water
-Lighter 16O isotope is more easily evaporated from seawater than 18O
-18O/16O ratio of seawater is higher during glaciations than interglaciations
-16O is trapped in the ice increasing 18O in the sea
-Fossil shells (foraminifera) with>18O were formed during colder glacial period and the other way round in ice cores would indicate warmer interglacial period