Past ecosystems Flashcards
Describe Ice Core Drilling
When ice is formed, gas bubbles in the water can be trapped when the liquid is solidified.
Gas remains chemically unchanged and contains information of the atmosphere at the time of solidification
Ice can contain dust, pollen, volcanic ash
Proves climate changes throughout history
State the stages of Fossilisation?
Rapid Burial, Fossilisation, either petrification or natural moulds, Uplift and weathering to expose fossils
Describe each stage of fossilisation
Rapid Burial:
-Living things buried by sediments in environment after they die
Fossilisation:
-Remains are preserved.
-fossilisation= no contact to oxygen (contact to oxygen=decomposition)
Petrification:
minerals replace body parts until remains are just fossil made of solid mineral. E.g. petrified wood
Natural Moulds:
Fossil remains are dissolved away by water, leaving only an impression in the rock (mould) some moulds are filled with minerals (casts)
Uplift and weathering to expose fossils
State the types of Fossils
Mould, Cast, Petrified Fossil, Carbon Film/ Carbonisation, Trace Fossil, Full Preservation
Explanation of each type of Fossil
Mould:
Hollow area in sediment which shows the shape of organism or part of organism
Cast: Solid copy of the shape
Petrified fossil: Fossils in which minerals replace all or part of an organism- also called per permineralisation
Carbon Film: Extremely thing coating of carbon atoms on rock- can preserve fine detail or no detail at all (coal)
Trace Fossil: Provide evidence of activities of ancient organisms e.g Coprolites (poo), burrows, footprints
Full preservation: remains of organisms with little to no change, organisms may have been trapped in tar, ice or amber
What are the conditions of fossilisation helping fossils survive
1: Quick Burial
2: Suitable body parts
3: Little geological disturbance
Features of each condition in fossilisation (what makes fossil survive)
Quick burial
prevents bones being eaten or scattered,
slows down the process of decay
keeps the organism parts generally intact
Suitable Body Parts
hard body parts survive better than soft parts (bones and teeth) few fossils before evolution of hard body parts 540 million years ago
Little geological disturbance
sediment rocks altered or destroyed by rock cycle over time
What can we learn/infer from fossils? provide CS
we can infer what an area was like ay the time of the fossil through distinct mineral and chemical signatures in layers
CS
King’s Canyon in NT- layer of curved sandstone sediments, indicating the sand dunes of a desert
What are banded ion formations
Geochemical evidence found in Australia
BIF’s are alternating bands of iron rich and iron poor sediments.
Show evidence for the change in composition of atmosphere from anaerobic to aerobic
First instances of photosynthesis
What are the 3 ways of Dating Geological events?
Superposition, Relative Dating, Absolute Dating
Describe the 3 ways of Dating Geological events?
Stratigraphy: uses the law of superposition to interoperate the stata
Relative dating: sedimentary rocks have to be in age order- correlates fossils from one area to another- by comparing
Absolute dating: Determined Analytically through precise measurements of the selected isotopes half life
Describe Radiometric dating
a process to determine the age of a fossil rock or minerals in years by measuring how many radioisotopes it contains compares to its decay product
parent isotope decays, releases energy and/or particles to become a more stable daughter atom.
carbon dating
describe half life
Different radioactive isotopes break down at predictable rates and break down into exactly half the number daughter as parent particles – this is the isotope’s half-life.
What is a Mass Spectrometer and what does it measure
measures the radioactivity of a sample
measures mass of isotopes
ratio of parent nuclide to daughter nuclide gives age of sample
