Lectures 2-5 Flashcards
Absolute date
A quantification for how old something is (albeit with error)
Boulder clay
Glacial deposit
Cirque
Bowl-shaped cavity on hillside with steep, cliff-like tops and shallow bottoms formed by ice
Daughter element
Element produced by radioactive decay
Devensian
The last glacial period (70Ma)
Diatom
Single-celled alga (aquatic plant) with a wall of silica
Dropstone
Large rock in fine-grained sediment thought to have been deposited by falling from a melting iceberg
Foraminifera
Single-celled aquatic animal with a CaCO3 shell
Freeze-thaw
Weathering that results from the expansion and contraction of material as it experiences temperature fluctuations around 0C
Gondwanaland
An ancient supercontinent
Green house
When Earth is relatively ice-free
Half-life
Time taken for one half of the original number of radioactive atoms to decay
Holocene
Last 11.7ka interglacial period (in which we live)
Horn
Three or more cirques back-to-back
Ice house
When Earth had ice at least covering high latitudes
Ipswichian
Penultimate interglacial period
Isotopic Age
Time since the isoptopic clock was ‘reset’ when isotopes were locked into the minerals (ie crystallisation after melting)
Late-Cenozoic Ice Age
Most recent ice age (that we live in)
Ordovician Ice Age
3rd-most recent ice age
Palaeontology
Study of fossils
Palynology
Study of pollen (organic microfossils)
Palynomorphs
Pollen grains
Periglacial
Areas surrounding glaciated regions
Permafrost
Permanently frozen ground
Permo-Carboniferous Ice Age
2nd most recent ice age
Phanerozoic
Last ~20% of Earth’s history, during which life boomed
Pingos
Uplifted frozen hill of permafrost
Polygons
Patterned ground formed through ice wedge action in permafrost regions
Precambrian
First ~80% of Earth’s history (little life present)
Radioactive decay
Spontaneous disintegration of a radioactive element (parent) to a different element/isotope (daughter), giving off energy in the process
Radiogenic
Formed by radioactive processes
Radiometric dating
Use of isotopes to provide absolute dates
Relative date
How old something is in comparison to something else
Snowball Earth
Theory that Earth was completely covered by ice
Stone circles
Concentric circles of rock, created in permafrost regions
Stratigraphy
Study of rock layers
Talik
Area of unfrozen ground surrounded by permafrost
Till
Glacial deposit
Tuya
Volcano that erupted underneath a glacier but melted through ice
Varves
Regular alternations in lake sediment layers
Vesicularity
Amount of gas bubbles in magma/lava
Volatiles
Volcanic gases
Geologic calendar/timescale
Chronology of events on Earth based on obtaining ages of past events