chapter10 Flashcards
a scientist that studies fossils is called what?
paleontologist
gradual change in living things over long periods of time is called
evolution
radioactive dating is used to do what
determine the absolute age of rocks
what happens during radioactive decay
atoms of one element break down to form atoms of another element
the half life of a radioactive element is what
time it takes for half of the radioactive atoms to decay
when all the atoms of a particular type of matter are all the same it is called
element
what is the law of superposisition used for
determine the realtive age of rocks
in a horizontal sedimentary rock what is at the bottom
the oldest layer
magma that forces its way into rocks and hardens is called what
intrusion
what is intrusion
a hardened layer of magam beneath Earths surface
what is extrusion
hardened layer of lave on Earths surface
what do fossils provide us
evidence of changes in Earths surface, how environments on Earth have changed over time and how groups of organisms have changed over time
when do most fossils form
when organisms die and are buried in sediment
mold,cast,petrified fossil, carbon film trace are all types of what
fossils
is a cast a solid copy of the shape of an organisms?
yes
true or false: a mold is a hollow are in sediment in the shape of an organism
true
true or false: molds and cast are the least common types of fossils
false: the are the most common
true or false: carbon film consists of an extremenly thick film of carbon on rock
false: thin film
trace fossils provide evidence of what
activities of ancient organisms
when does a petrified fossil form
when minerals replace all or part of an organism
where are fossils almost always found
sedimentary rock
the relative age of a rock is what
the age of the rock compared to ages of other rocks
why are index fossils useful
they tell the Relative ages of rock layers
the absolute age of a rocks is what
number or years since the rock formed
index fossils are used to what
determine relative age of rocks and are widely distributed throughout the world
what are ammonities
group of hard shelled animals the evolved in shallow seas more that 50,000 years ago. used as index fossils
geologist often use carbon-14 to do what
date materials that lived up to about 50,000 years ago
geologist use potassium-40 to do what
date rocks that are older than 50,000 years
the record of life forms and geologic events in Earths history is called what
geologic time scale
geologic time between precambrian time and today is divided into what
3ears
each era is also divided into what
periods
when did the earliest forms of life appear
precambrian time. similiar to bacteria of our time
in the cambrian explosion a great number of ___________evolved
organisms
when did plants and animals first reach land
paleozoic era
most fossilo fuels (primary coal) formed during which period
carboniferous
what formed during the permian period
pangaea
when did vertebrates arise
during ordovician & silurian periods
animals without backbones are called invertebrates. what are animals called with backbones
vertebrates
when did dinosaurs rule the Earth
mesozoic era. often called the age of reptiles
reptiles eveolved from what
amphibians
a gap in the geologic record is called what
unconformity
name all 4 eras:
cenozoic,mesozoic,paleozoic and precambrian time
in quaternary how many years ago and duration (millions of years)
1.8 million years ago and 1.8 to present is duration
tertiary what is its duration
65
cretaceous years and duration
66.4 and 78 is duration
jurassic years and duration
144 and 64 is duration
triassic years and duration
208 and 37 is duration
permian years and duration
245 and 41 is duration
carboniferous years and duration
285 and 74 is duration
devonian years and duration
360 and 48 is duration
silurian years and duration
408 and 30 is duration
ordovician years and duration
438 and 67 is duration
cambrian years and duration
544 and 544 million to 4.6 billion years ago
