Science Quiz - Fossils and Rock Dating

name for a scientist that studies fossils

paleontologists

dfference between trace and body fossil?

trace fossils are fossils made from traces/evidence left by an organism. body fossils are fossils of a body part of an ancient organism

how are fossils formed?

when organisms/their traces are buried by sediment

why is fast burial better

organism/trace is less likely to be destroyed and exposed to elements

what can keep dead organisms from becoming fossils?

decomposers can break them down before they harden into fossils. scavengers, physical factors like weather

is a jellyfish or mouse more likely to be fossilized and why?

mouse because it has a back bone and hard parts, jellyfish is soft parts and has no backbone

why is it hard for an organisms in a rainforest to become a fossil

large amount of rain throughout year causes rapid decay of dead organisms. decomposers and scavengers break them down quickly. hot temperature

three factors to consider in the process of fossilization?

avoiding scavengers and decomposers, having hard body structures, and dying in the right place

four ways that geologic processes can destroy a fossil once it’s formed?

fossils can get crushed, melted, moved, or eroded

why isn’t igneous rock a good place to look for fossils?

the rock is produced when lava cools and solidifies, so the extreme hot temps would destroy the organism.

two things to keep in mind when looking for a fossil?

fossils need to be in the right type of rock, and people need to look in the right place to find rocks of the right age.

draw the review chart of the steps to fossil formation and discovery!

organism dies. from there it can be destroyed, covered, or decomposed. if the organism is covered, then it can be destroyed or fossilized. if it is fossilized it can become destroyed, discovered, or stays buried.

relative order of events meaning

something that shows the order events happened in (earliest to most recent) but it doesn’t tell us actual or exact dates

Law of superposition meaning

states that in horizontal sedimentary layers, oldest rock layer is at the bottom and newest one is at the top

periods on geologic time scale represent…

biodiversity-changes in life forms

6 types of fossils

carbon film, preserved remains, petrified, cast, mold, trace fossils

what is carbon film

an extremely thin coating of carbon on rock

what are preserved remains

whole organisms/parts of organisms that have been preserved with little or no change

what are petrified fossils

fossils in which minerals replace all or part of an organism and then harden

what are cast fossils?

solid copy of the shape of an organism (cast is a filled in mold)

what are mold fossils?

hollow area in sediment in the shape of an organism/part of an organism

what are trace fossils?

preserved evidence of the activities of ancient organism

What is an intrusion?

MAGMA that pushes up from underneath, rock layers around it are older (only younger than the layers it goes through)

What is an extrusion?

LAVA that hardens on the surface, rock layers below are older

what are index fossils used to determine?

the relative age of rocks

what are characteristics of the BEST index fossils?

organisms that existed for a brief time but are widespread

in a long time, ____ will be a GREAT index fossil.

humans

what is relative age

the age of a rock or fossil compares to other rocks

relative dating provides an ____ of age based on the idea that _____

estimate, newer rock layers will cover the old ones

what is unconformity

a gap in the geologic record (missing layers)

what is a fault

a break in the Earth’s surface, only younger than the layers it splits

what are index fossils

fossils used to help date other fossils

half life meaning

the time it takes for half of the atoms in a sample to change into a new element

absolute age meaning

actual # of years since a rock was formed

everythig you see, including rocks is made of small particles called ___

atoms

radioactive decay is when… and example?

atoms of one element release energy causing them to change and form atoms of another stable element. ex- carbon 14 into nitrogen 14

radioactive dating- what does it provide based on what?

provides numerical age based on a comparison of the amount of the original element with the amount of new/stable element in the rock

___is used to date new fossils because…

carbon-14 because the half life is relatively short

___is used to date old fossils because…

potassium-40 because the half life is significantly long

radioactive dating cannot be used accurately for _____ rocks because

sedimentary rocks because they are made of sediment and sediment is all different ages