CLIMATE: L5 Reconstructing environmental change

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  • Created by: Elena
  • Created on: 02-04-14 16:57
What are the 5 main ways of reconstructing environmental change
Sediments, Depositional environments, Soils, Change in fauna and flora, and dating
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WHY? What can the past tell us about the climate?
Natural variability in the environment, rates of change, linkages (actions in one place can trigger events elsewhere), basis for modedlling future predictions, tell us of human impact
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What are the main patterns of the quaternary?
2.6mil years. Dominated by ice ages, repeated growth and decline of continental ice sheets, enormous env change close to and away from ice sheets.
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What is stratigraphy? - what 4 components make up stratigraphy?
the study of sediments and the sequence recorded in them. succession of facies, sedimentary record of events. lithography, biostratigraphy, chronostratigraphy, morphostratigraphy
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what is lithostratigraphy?
ordering of sediments through observations in lithology (physical characteristics of rocks). colour, composition, texture.
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what is biostratigraphy?
ordering of sediments through fossils - used more for interglacials - more fauna and fauna presence than during glacials
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what is chronostratigraphy?
based on dated levels eg C14 dating.
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what is morphostratigraphy?
not based on sediments but LANDFORMS. - chronological division of landforms based on their relative age and surface form.
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what two groups can sediments be classified as?
clastic (broken/old rock) and biogenic (produced by living organisms)
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What is the difference between facies and lithofacies?
facies are sediment body defined by genetic charateristics, lithofacies are defined by non genetic features
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How can lithofacies be observed
grain size/sorting, internal structures (can identify folds, strange layering), inclusions, bed thicknss,
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Depositional environments: we can look at sedimentary beds and bedforms - define this
sed beds - layers or strata (1cm thick), bedforms are deposited at zone between transporting medium and bed.
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what is are rhythmites?
cyclic repetitions (fine sediments, seasonal varves or surges of sediment)
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what 2 types of graded bedding are there?
normal (fining upwards), and inverse (coarsening upwards)
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what 2 types of mass flow deposits are there? (d and t)
debris flow (subaerial, subaqueous) and turbidity currents
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Soil dvpt. What are soils?
product of interaction between env conditions at earths surface and the lithosphere.
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What is Palaeosol (& buried peat)
past dvpt of soil vegetation
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Changing flora: what is palynology
reconstructing former vegetation cover from pollen grains in sediments
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How can we look at changing fauna?
megafauna - large fossils, and insects - abundant (coleoptera & chironomids) and human remain and artefacts.
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What are two main ways of classifying dating techniques?
absolute (ages assigned) and relative (ranking in order of age)
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Absolute dating example - eg 14C. how does it work?
RADIOMETRIC METHOD. radioactive decay of unstable isotopes. death of organism - tissue decay - decay of 14C. then measure remaining 14C to calculate age.
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Probems with c14 dating?
variations in 14c leads to underestimations of true age. Also contamination (addition of old carbon)
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Relative dating example.
LICHENOMETRY. eg gravestones. assume there is direct relationship between lichen size and age (also eg morraine, scree, rock glaciers.) need to know lichen growth rate and colonization lag period.
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Other cards in this set

Card 2

Front

WHY? What can the past tell us about the climate?

Back

Natural variability in the environment, rates of change, linkages (actions in one place can trigger events elsewhere), basis for modedlling future predictions, tell us of human impact

Card 3

Front

What are the main patterns of the quaternary?

Back

Preview of the front of card 3

Card 4

Front

What is stratigraphy? - what 4 components make up stratigraphy?

Back

Preview of the front of card 4

Card 5

Front

what is lithostratigraphy?

Back

Preview of the front of card 5
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