5- interpreting past environments

Question 1

what frameworks are needed to understand a past environment

Answer 1

1) temporal framework

2) spatial framework

Question 2

how is the temporal framework assessed

Answer 2

• scientists have worked out a stratigraphical column
• each time period is divided into stages , sub stages and bio-zones
• better resoulotion the younger the time period, if you go all the way back to pre-cambrian temporal framework gets alot larger

Question 3

how is the spatial framework useful

Answer 3

• explains continental configuration in each time period
• looks at remnant magnetism found in rocks (that lines up with poles) , helps to work out longitudinal location of fossils
• by doing this around the world can create a map of locations
• once you have a base map, this can be applied to different time periods
• E.g. when looking at early Triassic spatial framework was v different (pangea)
• sea level and continental config have changed throughout planets history

Question 4

how has the planets environment fluctuated throughout time

Answer 4

• no O2 in atmosphere originally
• O2 + Co2 levels fluctuate , thus temp fluctuates
• icehouse world vs greenhouse world

environment of planet earth has changed both in long and short term and life has had to cope.

Question 5

what discovery helped understanding of changing sea, ice and co2 levels

Answer 5

discovery of the ozone layer and how Co2 levels affect it helped understanding of changing global conditions

Question 6

what 5 techniques are used in interpreting past environments

Answer 6

1) nature of sediments ( relate to present day distribution)
- sedimintologists study how sediments form , see what conditions create what etc
2) nature of fossil content (relate to present day distribution)
3) distribution of climatically sensitive sediments
- certain rocks/sediments are only found in some environments, E,g, coal only found in cool temp environments
4) Environmentally discriminating isotopes
- isotopes should be present in constant levels in organisms , some are discriminated against. E.g. rubisco only takes in C12 , other organisms may need alot of calcium to build shells/bones
5) Environmentally influenced characteristics of organisms
- e.g gorwth rings only occur in trees that have a cold + hot season as they stop growing for part of the year
- organisms living in salt vs freshwater have diff characteristics

Question 7

how is climate modelling useful

Answer 7

• by understanding climate patterns of modern world you can then try and model climates of different time periods
• this can be done independently and then checked against other 5 methods to see if it fits

Question 8

Case study : environments in which dinosaurs lived

Answer 8

• dinosaurs were mainly around in the triassic period (continents=Pangaea) this allowed them to spread easily v few barriers (except mountain ranges)
• there was no ice at the poles (greenhouse world) , increased temp, co2 and sea levels
• by late jurassic continents started to fall apart, high sea levels flooded continents creating epicontinental shallow seas
• by KT boundary continents were separate

Question 9

sea levels were only lower then today in what time slice

Answer 9

permian

Question 10

Case study: polar dinosaurs

Answer 10

• poles experience extreme weather conditions
• 6 months of total darkness + 6 months of total sun
• during greenhouse world co2 levels were really high
• it was plotted where fossils were first found and a bunch of localities were inside the arctic circle
• thought that continental drift (spitsburg would have been more south) accounted for this
• Didn’t describe the distribution of other fossils found in arctic circle (where ti was supposedly too cold for reptiles)
• initial thoughts went to migration or hibernation, however no bone lags found and some dinosaurs were too small for migration
• knew it was cold due to ice structures found in fossil leave n bones
• possible evidence for migration in north but impossible in south
• had large eyes for suitable for polar winter

Question 11

The evidence for polar dinosaurs that didnt migrate or hibernate resulted in what question being asked

Answer 11

could some of the dinosaurs been warm blooded ?

• birds are warm blooded and they evolved from dinosaurs
• also now known alot of dinosaurs had feather like structures that may have been used in warmth
• also found that other reptiles are absent in many of the polar sites