History of the Earth Flashcards
_______ deals with the study of any layered (stratified) rock
Stratigraphy
Stratigraphy deals with the study of any layered (stratified) rock, but primarily with sedimentary rocks and their
composition, origin, age relationships, geographic extent
Many igneous rocks such as a ______ of lava flows, or ash beds
succession
Many igneous rocks such as a succession of lava flows, or ash beds are _____ and obey the principles of stratigraphy
stratified
Many metamorphic rocks are _______
stratified
Used to determine whether an object or event is older or younger than other objects or events
relative dating
What type of rock is used in relative dating?
sedimentary rocks
Sedimentary rocks are used in relative dating because:
- Formed from fragments of other type of rocks
- New rock layers are almost always flat
- Fossils are deposited in these layer of rocks
To deduce the geological history of the Earth, there are ideas or laws that need to be considered
law of original horizontality, law of superposition, principle of cross-cutting relations, unconformities
Principle of Original _____ states that layers of sediments deposited horizontally under action of gravity.
horizontality
(super = _____; positum = _____)
above; to place
simply states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.
law of superposition
Layering of rocks from oldest to youngest described by principle of _________.
superposition
The principle of _________ states that geologic features that cut across rocks must form after the rocks they cut through.
cross-cutting relations
The ____ is a tabular mass of igneous rock that cuts through the surrounding rocks
dike
The dike is a tabular mass of igneous rock that cuts through the surrounding rocks. The magmatic heat from igneous intrusions often creates a narrow “_____” zone of contact metamorphism on the adjacent rock, also indicating that the intrusion occurred after the surrounding rocks were in place.
baked
an igneous intrusion is younger than the rocks that are included
Cross-cutting dike
It shows a mass of rock that is offset by a fault, a fracture in rock along which displacement occurs. It is clear that the rocks must be ____ than the fault that broke them.
older
the rocks are older than the fault that displaced them
cross-cutting fault
Throughout Earth history, the deposition of sediment has been interrupted over and over again. All such breaks in the rock record are termed ______.
unconformities
An _______ represents a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed.
unconformity
There are three basic types of unconformities: __________________________________
angular unconformities, disconformities, and nonconformities.
the layers on either side of this gap in the rock record are essentially parallel
disconformity
younger sedimentary rocks rest atop older metamorphic or igneous rock
nonconformity
An _____ unconformity represents an extended period during which deformation and erosion occurred.
angular
Any method of measuring the age of an event or object in years.
absolute dating
Determining the actual age of an event or object in years.
absolute dating
To determine the absolute ages of fossils and rocks, scientists analyze ______ of radioactive elements.
isotopes
By adding together the number of protons and neutrons in the nucleus, the mass number of the atom is determined. The number of neutrons in the nucleus can vary. These variants, called _____, have different mass numbers.
isotopes
:forms of elements with different atomic mass.
Isotopes
For a given element the atomic number remains the ______, therefore the _____ of neutrons is different.
same; number
The forces that bind protons and neutrons together in the nucleus are usually ____.
strong
As a result, the nuclei spontaneously break apart (decay) in a process called ______.
radioactivity
_________: isotopes of elements that change spontaneously by losing or gaining subatomic particles.
Radioactive isotopes
For many isotopes the change from ____ element to stable _____ product does so through many steps.
parent; daughter
The path from parent element to stable daughter produce is termed the _______ for the parent.
Radioactive Series
Radioactive decay takes place at a ____ rate and has done so over all of geologic time
constant
Parent is ____ in amount.
Daughter product ____ iin amount.
At a ___ rate
reduced
increase
constant
Half-life of an isotope: the time taken for the amount of parent to be reduced by ___
½
Over successive half lives the parent is constantly ___ in amount and the daughter ____ in amount.
reduced; increases
Certainly among the most important properties of radioactivity is that it provides a reliable method of calculating the ages of rocks and minerals that contain particular radioactive isotopes. The procedure is called _________
radiometric(radioactive) dating.
The time required for one-half of the nuclei in a sample to decay is called the ___ of the isotope
half-life
_____ is a common way of expressing the rate of radioactive disintegration.
Half-life
In _________, an unstable radioactive isotope of one element breaks down into a stable isotope.
radioactive decay
,______ radioactive isotope is the parent isotope.
Unstable
Stable radioactive isotope produced by the radioactive decay of the parent isotope is called the ________.
daughter isotope
To date very recent events, ______ i used
carbon-14
Carbon-14 is the ________ of carbon. The process is often called ,_________.
radioactive isotope; radiocarbon dating
Because the half-life of carbon-14 is only ___ years, it can be used for dating events
from the historic past as well as those from very recent geologic history.
5730
In some cases, ____ can be used to date events as far back as _______
carbon-14; 70,000 years.
It is the remnant of any ancient animal or plant that has been preserved in rocks.
fossil
It is often the remains of the shell or bones in which minerals have crystallized.
fossil
The age of the fossil is ____ to the age of the rock on which it is found
equal
_____ provide clues to the prehistoric Earth and the organisms that existed.
Fossils
However, all fossils cannot be used as ______ fossil.
index
An index fossil must have the following properties:
• It must have had hard parts, like a shell.
• It must have lived over a short period on time, before it evolved into different creature.
• It must have lived all over the planet
types of fossil
Permineralization, Molds and Casts, Carbonization, Impression, Amber, Trace Fossils, Tracks, Burrows, Gastroliths
When mineral-rich groundwater permeates porous tissue such as bone or wood, minerals precipitate out of solution and fill pores and empty spaces
permineralization
The wood is gradually transformed into chert, sometimes with colorful bands from impurities such as iron or carbon.
permineralization
The word petrified literally means “turned into stone.”
permineralization
The word petrified literally means “_________.”
turned into stone
When a shell or another structure is buried in sediment and then dissolved by underground water, a mold is created. The mold faithfully reflects only the shape and surface marking of the organism; it does not reveal any information concerning its internal structure.
molds and casts
If these hollow spaces are subsequently filled with mineral matter, _____ are created.
casts
type of fossilization called _______ is particularly effective in preserving leaves and delicate animal forms.
carbonization
It occurs when fine sediment encases the remains of an organism. As time passes, pressure squeezes out the liquid and gaseous components and leaves behind a thin residue of carbon.
carbonization
f the film of carbon is lost from a fossil preserved in finegrained sediment, a replica of the surface, called an _______, may still show considerable detail.
impression
Delicate organisms, such as insects, are difficult to preserve, and consequently they are relatively rare in the ____________.
fossil record
Delicate organisms, such as insects, are difficult to preserve, and consequently they are relatively rare in the fossil record.
amber
Not only must they be protected from decay but they must not be subjected to any pressure that would crush them. One way in which some insects have been preserved is in ________, the hardened resin of ancient trees.
amber
different kinds of trace fossils
coprolites, tracks, burrows, gastroliths
animal footprints made in soft sediment that later turned into sedimentary rock
tracks
fossil dung and stomach contents that can provide useful Information pertaining to the size and food habits of organisms.
coprolites
ubes in sediment, wood, or rock made by an animal. These holes may later become filled with mineral matter and preserved. Some of the oldest-known fossils are believed to be worm _____.
burrows
highly polished stomach stones that were used in the grinding of food by some extinct reptiles.
gastroliths
