Earth's Origins Flashcards
relative dating
system for determining when rocks were formed and when geologic events happened in an area
relative age
the age of a rock as compared to others in the area
absolute age
the date the rock (or event) was actually formed
Principle of Superposition
Age-layering concept. To determine the ages and succession of geologic events and rocks, we assume that bottom layer of rock is oldest and each subsequent layer is younger than previous one
index fossils
a life form that lived a short period of time over broad area can be used as an index fossil. Its presence in sedimentary rock layers can help date the rock, giving a relative age
Correlation
A procedure showing that rock formation or geologic events took place at the same time in diff. locations
4 general methods of correlation
- use of index fossils
- observing erosion surfaces in rocks
- observing volcanic deposits (like ash)
- observing similar rock layer formations (like iron rich beds)
The modern method of estimating the Earth’s age is ____ decay. The element ____ decays to ____ with a half-life of ____ years as is used to date older rocks. The element used to date younger rocks is _____ with half-life of ____ years
radioactive uranium-238 lead-206 4.5 billion carbon-14 5700
half-life
time it takes for half of radioactive sample to decay
half-life of carbon-14 is approx. 5700 years. Starting with 100 grams, after 5700 years, 50 grams will have decayed. After the next 5700 years, 25 grams more will have decayed, etc.
How do scientists believe the Earth formed?
An exploding sun or solar nebula provided the hot gases tht formed the Earth. Its layers formed quickly as the gases condensed to liquid because of density variations. As the iron moved to the center of the proto-Earth, water was driven to the surface. The Oxygen for the atmosphere came indirectly from the water
Life on Earth probably began in ____. The first organisms were _____. The place where life began is referred to as the ____ soup. A reaction between ____ and ____ gas may have started life.
the ocean single-celled primordial lightning methane
Put the following living things in order:
mammals, amoeba, birds, fish, algae, amphibians, reptiles
amoeba algae fish amphibians reptiles birds mammals
species
All life forms that are able to interbreed and produce fertile offspring, e.g. cats, dogs, humans
Organic evolution
Theory states that there are variations of characteristics within a species, some of which increase the survivability of the organism. As these and other “desirable” qualities are passed to future generations, an entirely new species may evolve that cannot interbreed with the species from which it evolved
The remains of a once living organism are called a ___. They are usually trapped in ___rock.
fossil
sedimentary
fossil mold
original material of an organism preserved in sedimentary rock is completely removed, but an impression of its shape is left behind in the rock
fossil impression
the tracks of an animal walking on mud, or trails of earthworms
replaced remains
where the fossil remains have been replaced by another substance (like how petrified wood looks like the original cellulose but it is now made of silica)
layers of sedimentary rock deposited at diff. time periods are called ___. fossils specific to a time period are called ____ and may be used to date the rock.
strata
index (or guide) fossils
What is a scientist who studies fossils?
Paleontologist
the age of the Earth is ~ ____ years. Scientists divide this geologic time scale into ____, each of which is further divided into ____, which are divided into ____
5 billion
eras
periods
epochs
Pangaea
Most recent supercontient, composed of all the present-day continents; it began to break apart 200 mil years ago
Gondwanaland
southern part of Pangaea. Separated into Africa, Australia, Antarctica, Madagascar, India, S. America
Laurasia
N. part of Pangaea. Seperated into Europe, Asia, and N. America
