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Terms in this set (38)
Magma that forces its way into other rocks and hardens is called a(n)
A petrified fossil forms when
minerals replace all or part of an organism
the earliest forms of life appeared during?
on the geologic time scale, eras are divided into?
Fossils provide evidence for ?
1. changes in Earth's surface 2., how the enviroment has changed over time 3. how groups of organisms have changed over time
What was the Cambrian Explosion?
a great number of different organisms evolved
Most fossils form when organisms die and are buried in?
The mesozoic era is often called the ?
age of reptiles
Scientists use radioactive dating to?
determine the absolute ages of rocks
The most important differentiation of reptiles is?
having scaly skin and leathery shelled eggs
The gradual change in living things over long periods of time is called?
The _______ of a radioactive element is the time it takes for half of the radioactive atoms to decay
Fossils are found in what type of rocks?
Plants and animals first reached land during what era?
the earliest life forms were probably similar to present day ?
Dinosaurs ruled the Earth during what era?
Geologists often use ______ to find the absolute ages of rocks
potassium - 40
Animals without backbones are called ?
index fossils are useful because?
they can tell the relative age of rocks
What is the law of superposition used for
to measure the relative age of rocks
Casts form from ?
what era and period are we currently in?
Cenozoic Era, Quartenary Period
What are the two layers of igneous rocks?
1. extrusion 2. intrusion
extrusions are younger than the rocks?
intrusions are younger than the rocks?
Radioactive decay works on what kind of rocks?
Why doesn't radioactive decay work on sedimentary rocks
because sedimentary rocks are may rocks combined together
sediment is made up of
rock particles and living things
what are the 5 types of fossils ?
molds and casts , petrified fossil , carbon film , trace fossil , preserved remains
the most common fossils are?
molds and casts
The fossil record provides evidence about?
the history of life and part enviroments on Earth
How do you determine a rock's relative age?
extrusions and intrusions of igneous rocks
What are index fossils used for
they tell the relative ages of the rock layers in which they occur
most of Earth's geologic record has been lost due to ?
what can change the position in which rock layers appear?
gaps in the geologic record and folding
What are the 3 eras?
1, paleozoic 2, mesozoic 3. cenozoic
the oldest rocks on earth are how old?
4 billion years old
most fossils form when
living things die and are buried by sediment