Impacts Flashcards
What is the age of the earth? (schools of thought through time)
James usher thought earth was creased 4004 BC.
Uniformitarianists thought the present was the key to the past, and measured the rate of crust formation and how long it would take to form, thought millions of years.
Kelvin calculated rate of cooling from molten earth body, thought 20-40 million years. All wrong. THe earth is 4.55 billion years old!
Oldest rock is 4.04 Ga in Acasta Gness in NWT.
Found meteorites 4.55 Ga, dated using radioactive half lives.
What are the divisions of the geological time scale? write them out!
do it with the slides nicola!
What is the biosphere?
Thin layer of life on earht’s surface composed of ecosystems.
i.e. arctic ecosystem, interconnected.
Used to look very different (ordovician or cretaceous)
What is stratigraphy and biostratgraphy?
Stratigraphy: studying layers of rock (strata)
Biostratigraphy: identified relative ages of rock layers using fossils.
Time is recorded in layers of rock, helps us look at evolution of species through time, helps with passage of time on earth.
Who is James hutton?
Uniformitarianst who says present is the key to the past. Same natural laws and processes that operate in universe have always operated this way and apply everywhere.
Who is Nicholas Steno?
Principles of stratigraphy!
- Law of superpositoin: whats on top is youngest
- Principle of original horizontality: if its tilted or folded it used to be flat.
- Principle of lateral continuity: if its here its over there too
- Principle of cross cutting relationships: if it cuts through, its younger”
ie. dikes!
What is siccar point?
Great example of an unconformity: period of non deposition or active erosion. Tilted sediments originally deposited in a desert from devonian period, and verticle rocks containing marine fossils deposied in silurian next to each other with an unconformity in between.
What was the concept of extinction and who thought of it?
George Cuvier: established elephants were different species in different places (indian vs african) and conclued that mammoths used to be alive but become extinct.
IMPORTANT: people used to think fossils were just dead things, never though that htey were once alive.
Who is william smith?
Principle of faunal succession. FOssils succeed each other vertically in a specific order identifiable over long distances. CORRELATE OVER CONTINENTS.
Strata of the same age can be dated and correlated using their FOSSILS.
Only works because of evolution. Fossils must change for this to work.
What is an INdex fossiL?
Ideal species in biostratigraphy. needs 4 things
- A short range, to make higher resolution of age. i.e. ammonites are commonly used (251-66ma)
- common
- wide geographical distribution
- died in environments for good fossilization/preservation.
can correlate time using these index fossils.
When were the 5 major extinction events?
End of Cretaceous 65ma End of Triassic 205 ma Permian-Triassic 251ma Late devonian 360ma Late ordovician. 450ma
What is radiation of a new species?
after an extinction event, rapid diversification occurs into more species, mass extinctions make new resources available and creates more challenges: more NICHEs.
First appearance of new fossils helps geologists define start of a new period.
What is background extinction?
ALways some species are becoming extinct, a constand background level of extinction. Many things have become extinct since last ice age, currently rate is about 100 extincitons per million species per year.
- caused by humans? likely.
What defines a mass extinction?
30% of species lost
Broad range of ecosystems
Short/sudden. 1ma maximum
What is the order of taxonomy?
Kindom, Phylum, class, order, family, genus, species.
