Sea Level Change Flashcards
What is the principle control of tides?
Lunar cycles - the gravitational attraction caused between the earth and the moon and sun.
What happened to Galvestone Texas?
Hit by hurricane Ike in 2008, caused widespread flooding and was the 3rd costliest disaster to hit USA.
What 3 factors control the amount of sediment delivered to the coastal zone (fluvial)?
- the steepness of the catchment
- the size of the catchment
- the amount of precipitation within the catchment
What are the tectonic controls on sea level change?
- subsidence of the ocean basin
- uplift of the mid oceanic ridge
- increase/decrease in length of the mid ocean ridge system.
What is happening in the UK with regards to uplift/subsidence and why?
N UK is undergoing uplift at 3 mm/year whilst the SE of the UK is subsiding 1 mm/year. This is the result of isostaic uplift resulting from the compression of the lithosphere and asthenosphere as a result of loading of ice sheets during the last glacial period which compressed zones. With load removed the lithosphere is responding. Due to its rigid nature as one bit of the lithosphere rises one must fall.
What is thermal expansion?
This is the process whereby as atoms are heated they become more excited, moving faster and occupying a great space within molecules. This causes an expansion in their size. This process is responsible for modern day eustatic sea level rise - 2mm/yr
How does the concentration of oxygen isotopes vary?
The ratio of O2 isotopes varies depending on the extent of glaciation on the earth. The larger the area covered by ice the less 16O and more 18O found in the ocean.
16O is lighter than 18O and as a result is more easily evaporated from the ocean. Leading to higher concentrations of 16O in polar hemisphere ice.
How can Oxygen isotopes be used to determine sea level changes?
Equation :S18O = (18O/16O)sample - (18O/16O)SMOW
————————————————
(18O/16O) SMOW
samples taken from deep water deposits, assessing the oxygen isotopes within calcareous organisms.
What does it mean if S18O changes positively or negatively?
+ means that the ice sheets are expanding and so there is a lowering of eustatic sea levels.
- means there is a decrease in ice sheets and so an increase of global sea levels.
every 0.1 change = 10 m change.
What is the difference between relative and eustatic sea level change.
Relative sea level change is the change of sea level at a local scale due to uplift or subsidence of land, eustatic is the global change in sea level.
What evidence can we use to determine sea level changes?
oxygen isotopes, marine deposits on terrestrial environments, marine terraces (erosional features), marine coastlines that have been submerged.
How do facies sequences provide information on sea level changes.
Disambiguates within the sequences illustrates possibility of sea level change
Using marine terraces what would you need to evaluate height and age of previous sea level high stands.
- rate of uplift
- age of each terrace using isotopes within calcareous organisms
