Actual Fossils Test Flashcards
why did the other one have 43 cards
What is a fossil?
The preserved remains/imprints/traces of past life
What is petrified wood?
A type of fossilized wood where a tree/tree-like plant turned to stone by permineralization
In which rock type are fossils normally found?
Sedimentary rock
What causes fossils to be exposed at the surface?
Weathering and erosion
What replaces the organic matter and/or empty pore spaces in a fossil?
Minerals
Why is it important to study fossils?
Using fossils, you can determine the absolute and relative age of rocks. Fossils also provide clues to an areas ancient environment/weather/climate. They can show the evolution of present life, and they give us clues to past geologic events
What is catastrophism?
The idea that quick/sudden, violent events shaped the Earth and its organisms.
Why do scientists disagree with the idea of catastrophism?
They disagree because Earth’s history had a lot of violent events. Instead, they believe in catastrophism and the idea that slow process shape the earth as well.
What is uniformitarianism?
The idea that “Geologic processes that occur today are similar to those that have occurred in the past.”
Who came up with the idea of uniformitarianism?
James Hutton in the 1700s by observing how his farm changed over the years, and applied his evidence to the whole world.
What are the best conditions for fossils to form?
Being buried quickly (protection for destruction), hard body parts (teeth bones, shells), consistent temperatures and weather conditions, lots of minerals, and fine sediments.
What are the two types of fossil preservations?
Body fossil and trace fossil
What are body fossils?
The remains of part and/or all of an actual organism
What are trace fossils?
Fossilized traces or marks left behind by an organism
What are the types of trace fossils?
Trails and tracks, burrows, nests, footprints, coprolites
What are the types of body fossils? (5)
Permineralized remains, carbon films, coals, molds/casts, original remains
What is another name for permineralized remains?
Petrified fossils
What is mineral replacement?
“When minerals fill small holes in hard parts like bone, teeth & shells
How does something become permineralized?
First, minerals fill up the empty pore spaces/small holes in the organism. Then, water covers the fossil, and dissolves it. The minerals in the water then replace the dissolved parts of the fossil, and harden into a rock
What are carbon films?
When organisms or parts of an organism are pressed between layers of soft mud or clay and leave an imprint behind
How are carbon films formed?
An organism is first buried in soft mud/clay. Over time, the pressure and heat increases, causing most of the organism to decay. What is left is a thin layer of carbon, which is the carbon imprint.
What are coal body fossils?
Coal body fossils are formed when plant matter is accumulated. As more and more is accumulated, the heat and pressure eventually turn the matter into coal.
What is a mold?
When an organism is buried/covered by sediments, but water flows through the organism and dissolves it, leaving behind a cavity in the shape of the organism
What is a cast?
When groundwater flows into a mold and hardens inside, forming a copy of the organism
What are original remains body fossils?
When soft parts of an organism are preserved in amber, ice, or tar.
What are fossilized tracks?
A type of trace fossil (footprints) that can tell us the size, weight, age, and social behavior of an organism.
What are trails and burrows?
Trace fossils that are tunnels left behind by burrowing organisms, which can provide clues on how an animal lived.
What is the Principle of Superposition?
The idea that in layers of undisturbed rocks, the oldest rocks are on the bottom, and the youngest are on the top.
What is relative age?
The age of rocks and geologic features compared with other rocks and features nearby (can determine if rock is “younger” or “older”)
How do geologists determine relative age?
They observe the age of the rocks surrounding the rock they are trying to find the age of.
How is relative age and absolute age different?
Relative age can only determine if the rock is younger or older than the rocks surrounding it. Absolute age can narrow it down to years/time periods.
What is the Principle of Original Horizontality?
The idea that “most rock-forming materials are deposited in horizontal layers.” Even if they are deformed, they were still originally deposited horizontally.
What is the Principle of Lateral Continuity?
Rock layers are all deposited into continous sheets in all lateral directions, until they thin out or meet a barrier.
“For example] a river might erode the layers, but their placements do not change.”
What are inclusions?
When a piece of an older rock becomes part of a new rock
How are inclusions formed?
When a piece of an old rock falls into new-forming rock (sediments or magma), and the new rock hardens with the old rock in it.
What does the Principle of inclusions say about the age of the rocks?
The rock containing the pieces of the rock is the younger one
What is a cross-cutting relationship?
The principle that when a rock gets cut through, the thing doing the cutting (whether it be a fault, dike, or intrusion) is younger than the rock being cut
What are some examples of cross-cutting relationships?
Faults (“when rocks move along a fracture line, the fracture is called a fault”) and dikes
What does the principle of cross-cutting relationships say about the age of the rocks?
The geologic feature that gets cut is the older one
What is an unconformity?
When a layer of rock has been eroded and another layer is deposited on top of it, so it creates a gap in the fossil record.
How are unconformities formed?
A layer of rock is uplifted or exposed to the surface, and erodes away. A new layer is deposited on top, causing a gap in the record.
What are the 3 types of unconformities?
Disconformity, angular unconformity, and nonconformity
What is a disconformity?
“Younger sedimentary layers are deposited on top of older, horizontal sedimentary layers that have been eroded.” (stereotypical unconformity)
What is an angular unconformity?
“Sedimentary layers are deposited on top of tilted or folded sedimentary layers that have been eroded.”
What is a nonconformity?
“Younger sedimentary layers are deposited on older igneous or metamorphic rock layers that have been eroded.”
What is correlation?
When geologists match up rocks and fossils from different locations to fill in the gaps in the fossil record (gaps often caused by unconformity).
What is another word for correlation?
Connection
What are index fossils?
They are fossils that “…represent species that existed on Earth for a short length of time, were abundant, and inhabited many locations.”
Why are index fossils especially useful for determining the age of rock layers?
Index fossils represent short periods of time, so it is easier to find the relative age of rocks with index fossils.
What is one example of an index fossil?
Certain trilobites
Where are sedimentary rocks usually found?
Underwater
What is absolute age?
“The numerical age, in years, of a rock or object.”
What is an atom made up of?
Protons (positive charge and in the nucleus), neutrons (no charge and in the nucleus), and electrons (negative charge and around the nucleus)
What is an isotope?
“…atoms of the same element that have different number of neutrons.”
What is radioactive decay?
When a radioactive isotope (unstable isotope) naturally decays to form a stable isotope (can be the same element of a different one)
What is an unstable isotope that decays called?
Parent isotope
What is the new isotope/element that forms in radioactive decay called?
Daughter isotope
What causes an isotope to be unstable?
A certain number of neutrons
What happens to the extra neutron in the isotope?
It decays to form a proton
What is a half life?
“…the time required for half of the parent isotopes to decay into daughter isotopes.”
50% parent isotope and 50% daughter isotope
What is the ratio for one half life?
50/50
What is a ratio for 2 half lives?
25/75
etc…for more half lives
What is radiometric dating?
Since radioactive isotopes have a constant rate of decay, scientists look at the ratio of parent isotopes to daughter isotopes in the rock they want to date. Using half-lives, they can figure out the absolute age of a material.
What is radiocarbon dating?
Since the ratio for C-14 (radiocarbon) and C-12 in the atmosphere is that same for the ratio in living things, scientists can figure out the age of a dead organism based on the ratio of C-14 and C-12 in the organism to that of the atmosphere. This can only be used for living things, since they contain carbon.
About how old does a dead organism have to be for radiocarbon dating to be successful?
Up to 60,000 years old, since the half life of C-14 is 5,730
How do you date igneous and metamorphic rocks?
Using the unstable isotope uranium-235, which is found in crystallized magma. U-235 decays into lead-207 (Pb-207), so scientists use the ratio of U-235 to Pb-207 to see how long ago the rock was formed.
How do you date a sedimentary rock?
Sedimentary rocks are harder to date since they are made up of grains, which can come from all over the world and the grains could have been formed in different times.
How old is the earth?
About 4.54 billion years old
Who came up with uniformitarianism?
James Hutton
What is the geologic time scale/timeline?
An organization of the Earth’s past, split up into different units of measurement
What are the 4 major subdivisions in the geologic timeline?
Eons, eras, periods, and epochs
(in order longest to shortest)
How did scientists determine the geologic time scale?
They took note of abrupt changes in the fossils and rocks and the relative ages of rocks. Using that, they put the rocks in a certain order, which is the geologic time scale.
How many eons are there?
4
What are the 4 eons?
Hadean, Archean, Proterozoic, and Phanerozoic
(Order oldest to youngest)
What time do the first 3 eons make up? (Hadean, Archean, Proterozoic)
Precambrian time
What is precambrian time?
Precambrian time is 90% of Earth’s history, where unicellular organisms and soft-body organisms lived and unlike those today. Most died at the end of Precambrian time.
What was the Hadean eon?
It’s the eon of rocks from meteorites and the moon
What was the Archean eon?
The eon when the earliest rocks on Earth form
What was the Proterozoic eon?
The eon of organisms with well-developed cells
What is the Phanerozoic eon?
It’s the eon of visible life (has lots of life forms) and is well-represented in the fossil record. It is the eon we are living in today.
Which 3 eras make up the Phanerozoic eon?
Paleozoic, Mesozoic, and Cenozoic
(order oldest to youngest)
How do eras end?
With mass extinction
Which periods make up the Paleozoic era?
Cambrian, Ordovician, Silurian, Devonian, Mississippian and Pennsylvanian (Carboniferous), and Permian
(in order oldest to youngest)
What is the Cambrian period known for?
It is the first period after the Cambrian explosion, where the first trilobites were found.
What is the Ordovician period known for?
First vertebrates
What is the Silurian period known for?
First land plants
What is the Devonian period known for?
When the age of the fish flourished
What is the Mississippian period known for?
The period of winged insects
What is the Pennsylvanian period known for?
The first reptiles
What is the Permian period known for?
When the age of the amphibians flourished
What is the middle Paleozoic era known as?
Age of fish
What is the early Paleozoic era known as?
Age of the invertebrates
What is the late Paleozoic era known as?
Age of the amphibians
How did the Paleozoic era end?
- Volcanoes
- Climate change
- less space for marine life (pangaea)
What did the early Paleozoic consist of?
Animals that lived in the ocean and had no backbone (age of invertebrates)
What did the middle Paleozoic consist of?
Animals with backbones evolved.
Cockroaches, dragonflies & insects evolved on land. Earth’s 1st plants appeared, they were small & lived in water. Continents collided. Appalachian mountains formed. Age of fish.
What did the late Paleozoic consist of?
Amphibians adapted to land, but had to go back to the water to have babies. Reptiles evolved to where they didn’t need to lay eggs in the water. Coal swamps were thriving. Pangaea formed and climate cooled.
What is the Carboniferous period?
Mississippian period and Pennsylvanian period combined.
What were the 3 periods of the Mesozoic era?
Triassic, Jurassic, and Cretaceous
(order oldest to youngest)
What is the Triassic period known for?
The first dinosaurs/small mammals
What is the Jurassic period known for?
The first birds/flowering plants
What is the Cretaceous period known?
When the dinosaurs flourished
What are angiosperms?
Plants with flowers & seeds enclosed in their fruit
(female)
What are gymnosperms?
Plants with cones, no flowers or fruits; have naked, no protective covering seeds on the surface of their leaves
(male)
Which animals dominated in the Mesozoic era?
Dinosaurs and reptiles flourished, but mammals began to evolve
How is the Mesozoic climate different than the Paleozoic climate?
The climate was warmer because the ice caps melted. This also caused sea levels to rise, since the glaciers melting caused more water to be in the ocean. Additionally, the Rocky Mountains were formed during the Mesozoic era
What caused the end of the Cretaceous period/Mesozoic era?
Mass extinction by volcanic eruptions or a meteorite. This blocked the sunlight, causing most living organisms to die.
What periods make up the Cenozoic era?
Tertiary and Quaternary
(Oldest to youngest)
What is the Tertiary period known for?
When mammals thrived
What is the Quaternary period known for?
It’s the age of man/technology
What happened in the Tertiary period? (landscape-wise)
Earth’s continents continued to move, causing the Atlantic Ocean to widen.
India crashed into Asia forming the Himalayas, and Africa pushed into Europe, forming the Alps. The Rocky Mountains continue to grow. The Cascade & the Sierra Nevadas-formed on the West coast. Appalachian Mountains continue to erode.
What is an ice age?
when a large proportion of Earth’s surface is covered by glaciers
Which eon, era, period, and epochs do we live in today?
Phanerozoic eon, Cenozoic era, Quaternary period, and Holocene epoch
How did Precambrian time end?
4.5 b - 544 mya
Ended due to climate/weather/environment changes, likely an ice age
In which era do humans appear/live in?
The Cenozoic era
What types of fossils were found from Precambrian time?
Rare fossils of soft bodied organisms
Why weren’t there a lot of fossils in Precambrian time?
The organisms did not have hard body parts, making it harder for them to fossilize
What is the Mesozoic era known as?
The age of reptiles/dinosaurs
What is the Cenozoic era known as?
Age of mammals
What is an intrusion?
A cross-cutting relationship where magma “intrudes” into a rock and hardens there
How are intrusions and inclusions related?
An intrusion happens first, with magma “intruding” on a pre-existing rock. While forming, the younger rock picks up pieces of the pre-existing rock, which is known as an inclusion.
How can you determine the age of a rock if the rock layers are turned?
You can look at the fossils (index fossils) in the rock layer, then, using correlation, you can tell the relative of the rock layers
What can cause rock layers to no longer be horizontal?
Earthquakes, mountain building, uplift, etc.
What are the “requirements” to be considered an index fossil?
You have to be abundant, widespread, and short-lived
How do scientists match up rock layers?
Correlation (“matching rocks and fossils from separate locations”)
How is absolute age found?
Using radioactive decay, radiometric dating, and radiocarbon dating
What are some slow, everyday processes?
Tectonic plates moving, glaciers, and ice age
What are some violent, unusual events?
Volcanic eruptions, earthquakes, etc.
What can fossils tell us?
When, where, and how organisms lived
What can fossils not tell us?
Color, sounds, and behavior of the organism
What are some examples of catastrophic events?
Volcanic eruptions, flooding, etc.
What were the periods in the early Paleozoic?
Cambrian and Ordovician
What were the periods in the middle Paleozoic?
Silurian and Devonian
What were the periods in the late Paleozoic?
Carboniferous and Permian
When were the Appalachian Mountains formed?
Middle Paleozoic
When were the Rocky mountains formed?
The Mesozoic era
When are the Himalayas formed?
The Cenozoic era
When does Pangaea break apart?
Mesozoic era; Triassic period
What was the Pleistocene epoch?
The first epoch in the Quaternary period
When are the Alps formed?
Cenozoic era
When are the The Cascade & the Sierra Nevadas formed?
Cenozoic era
What kinds of mammals lived in the Cenozoic era (other than humans)?
Woolly mammoth, giant sloths, saber-toothed cats
What happened during the Pliocene and Pleistocene epochs (weather-wise)?
Ice age
Why do species become extinct?
They cannot adapt to a new environment
How many fossils do the oldest rocks on Earth contain?
A few
When did Pangaea form?
In the Carboniferous period (Middle Paleozoic)
What is organic evolution?
The changing of organisms over geologic time
What is cyanobacteria?
A bacteria that is thought to be one of the earliest life forms on Earth
In which era do dinosaurs, birds, and flowering plants appear in?
Mesozoic era
When did small mammals first appear?
Mesozoic era; Triassic period
