fossils and geo time scale Flashcards
What is a fossil?
A fossil is the natural remains or evidence of living things from prehistoric times typically over 10000 years old to be classified as a fossil
Who studied fossils?
Palaeontologists do, to learn more about and understand earth’s past
What do fossils show us?
Fossils reveal how organisms have changed over time, providing evidence of species and evolutions and indicate environment and climate changes in history.
How are fossils formed?
Fossils are formed when dead plants or animals are buried under layers of sand and mud. Over time, pressure turns these layers into sedimentary rock, and minerals replace the organic matter creating a stone replica
What happens to fossils over time?
They can be eroded out of the rock, but most remains are lost during this process.
What is uplift in geology?
Upmost is the process where underground rocks rise to earth’s surface - fossils become more accessible
What is mineralisation?
When an organism dies and is buried under sand and sediments. Over time, minerals replace the original material, leaving only minerals behind.
What is carbonisation?
Happens when a dead organism is compressed over time, causing gases to escape and leave a carbon outline of the organisms remains
What are miles and casts?
An impression left by a hard part of an organism (like a deep imprint) A case is when the mild fills with sediment or minerals, creating a 3D replica
What are trace fossils?
Provide evidence of an organisms activity or behaviour such as footprints or bite marks.
What are preserved remains?
Organisms that have been found intact in a suitable environment for thousands of years, such as those in amber or ice
How can geological history be interpreted from sedimentary rocks
Using the law of superposition, states that in undisturbed layers older fossils are in bottom layers and vice versa. Disturbances like earthquakes volcanic activity and human activity can disrupt layers and provide insight into geological events
What are index fossils?
Index fossils are the remains of organisms that lived during a specific geological age, used to identify and date the age of strata in different locations
Two main rules of relative dating?
Law of superposition : In undisturbed layers, older rocks are at the bottom and younger rocks are at the top.
Law of faunal succession : fossil species are in a specific recognisable order in the same layer
What classifies and index fossils?
Distinctive, globally widespread and abundant
What are strata?
Layers of sedimentary rock that have distinct characteristics helping identify and date geological events
What is stratigraphy?
Comparing rock layers in different locations
What is a fluorine analysis?
Determines the relative age of bones and artefacts by measuring the amount of fluorine they can contains, which increases the longer they’re buried.
What is absolute dating/ radioisotope dating?
Absolute dating determines the age of fossils by measuring the remaining radioactive isotopes they contains. An isotopes half life is how long it take for half the original isotope to decay
How are periods measure in the geological time scale?
By millions (mya)
What was the first period in the time scale?
Precambrian, dominance of bacteria
What is the palaeozoic era
Animals with shells, 6
Period
What is the Mesozoic era?
Age of reptiles, 3 periods : Jurassic, Cretaceous, Triassic
Which era do we currently live in?
Cenozoic era, tertiary and quaternary
How many major eras are there
Palaeozoic, Mesozoic, cenozoic
what are the 4 types of fossils and their meaning?
Original : when a part of an organism is preserved, with its chemical composition being similar to when it was living
Replacement : When a part of the organism is chemically changed into another mineral
Carbon Film : When the dead part of the body decays and leaves a black deposit of carbon
Indirect : evidence of remains such as imprints, molds, casts
What are the five types of preservation environments for fossils and the best type
Marine environments, cause more sediment and mud. 5 types are permafrost, tar, amber, peat and dry air
What are the five types of preservation environments for fossils and the best type
Marine environments, cause more sediment and mud. 5 types are permafrost, tar, amber, peat and dry air
Why is the fossil record incomplete
Because some fossils are not based in marine environments and may have eroded
What is tree ring dating
Counting growth rings in wood chunks of of trees
What are transitional fossils
Fossils that exhibit characteristics from both its ancestral and derived form
