Unit 4

Question 1

a principle that geologic processes that occurred in the past can be explained by current geologic processes

Answer 1

Uniformitarianism

Question 2

the age of an object in relation to the ages of other objects around it

Answer 2

Relative age

Question 3

the principle that a sedimentary rock layer is older than the layers above it and younger than other layers below it if the layers are not disturbed

Answer 3

Law of Superstition

Question 4

sedimentary rocks left undisturbed will remain in horizontal layers: rocks are deposited horizontally, if something is altered it was done so after the rock formed

Answer 4

Principle of Original Horizontality

Question 5

a break in the geologic record created when rock layers are eroded when sediment is not deposited for a long period of time

Answer 5

Unconformities

Question 6

an igneous intrusion is always younger than the rock it cuts across.

Answer 6

Law of Crosscutting Relationship

Question 7

the numeric age of an object or event, often stated in years before the present, as established by an absolute-dating process, such as radiometric dating

Answer 7

Absolute age

Question 8

One way to study absolute age
Ex: If scientists can measure the rate at which as stream erodes its bed, then they can estimate the age of the stream
This is practical only for geologic features formed within the past 10,000 to 20,000 years.

Answer 8

Rates of erosion

Question 9

what are the methods of absolute dating?

Answer 9

Rates of erosion
Rates of deposition
Varve count
Radiometric dating

Question 10

way of studying absolute age
Another way to estimate absolute age is to calculate the rate of deposition.
In general, about 30 cm of sedimentary rock is deposited over a period of 1000 years.
Note dramatic things can occur that changes the average rate such as a flood which would throw average off

Answer 10

rates of deposition

Question 11

way of studying absolute age
a pair of sedimentary layers (one of coarse, one fine) that is deposited in an annual cycle, commonly in glacial lakes and that can be used to determine absolute age

Answer 11

varve count

Question 12

way of studying absolute age
a method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope
Recall atoms of the same element that have different numbers of neutrons are called isotopes
Using the known decay rate for a given element scientists can determine the amount of time required to produced the proportions of parent and daughter isotopes; the known decay rate is typically recorded as a half-life

Answer 12

Radiometric Dating

Question 13

the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope

Answer 13

Half life

Question 14

he determination of the age or date of organic matter from the relative proportions of the carbon isotopes carbon-12 and carbon-14 that it contains

Answer 14

Carbon dating

Question 15

How do fossils form?

Answer 15

Sediments cover fossils slowing/stopping decay and protecting the sample from damage
Normally, dead plants and animals are eaten by other animals or decomposed by bacteria. Only dead organisms that are buried quickly or protected from decay can become fossils.
Typically only hard parts of organisms can become fossils. (bone, shells, teeth, ect)

Question 16

What are the types of fossils?

Answer 16

body fossils, trace fossils,index fossils

Question 17

remains of the body parts of ancient animals, plants, and other life forms
Include: Carbon films, molds, casts, ect.

Answer 17

Body fossils

Question 18

a fossilized mark that formed in sedimentary rock by the movement of an animal on or within soft sediment
Include: gastroliths, burrows, footprints, and coprolites

Answer 18

Trace fossils

Question 19

fossil that is used to establish the age of rock layers because it is distinct, abundant, and widespread and existed only for a short span of geologic time
Scientist can use index fossils to estimate the absolute ages of specific rock layers. Because organisms that make up index fossils only existed for a specific time period we can assign an accurate age of the rock.

Answer 19

index fossils

Question 20

an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom

Answer 20

geologic column

Question 21

is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth’s history.

Answer 21

geologic time scale

Question 22

the largest unit of geologic time

Answer 22

eon

Question 23

a unit of geologic time that includes two or more periods

Answer 23

Era

Question 24

a unit of geologic time that is longer than an epoch but shorter than an era

Answer 24

Period

Question 25

a subdivision of geologic time that is longer than an age but shorter than a period

Answer 25

Epoch

Question 26

defined the occurrence of distinct fossils in the fossil record

Answer 26

Age

Question 27

the process of change by which new species develop from preexisting species over time

Answer 27

Evolution

Question 28

a geologic eon of the Earth predating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended about 4 billion years ago
Comes from the greek Hades
Literally means “hell” on Earth
was in the Precambrian time

Answer 28

Hadean Eon

Question 29

is one of the four geologic eons of Earth history, occurring 4,000 to 2,500 million years ago
During this, the Earth’s crust had cooled enough to allow the formation of continents and life started to form.The processes that gave rise to life on Earth are not completely understood, but there is substantial evidence that life came into existence either near the end of the Hadean Eon or early in the this Eon.
The earliest identifiable fossils consist of stromatolites
was in the Precambrian time

Answer 29

Archean eon

Question 30

a geological eon spanning the time from the appearance of oxygen in Earth’s atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth
The well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; several glaciations, which produced the hypothesized Snowball Earth during the Cryogenian Period in the late Neoproterozoic Era
The Ediacaran Period (635 to 541 Ma) which is characterized by the evolution of abundant soft-bodied multicellular organisms and provides us with the first obvious fossil evidence of life on earth.

Answer 30

Proterozoic eon

Question 31

Earth gradually assumed its present configuration and physical features through such processes as continental drift, mountain building, and continental glaciation.

Answer 31

Phanerozoic eon

Question 32

fish diversified and marine organisms were very abundant. In North America, the Paleozoic is characterized by multiple advances and retreats of shallow seas and repeated continental collisions that formed the Appalachian Mountains

Answer 32

Paleozoic era

Question 33

marked a profound change in life on Earth; prior to this period, the majority of living organisms on the whole were small, unicellular and simple.
Complex, multicellular organisms gradually became more common in the millions of years immediately preceding this period, but it was not until this period that mineralized—hence readily fossilized—organisms became common
Marine invertebrates, no backbone, thrived in the warm shallow seas
Common animals in this period:
Trilobites
Brachiopods
Ancient relatives of jellyfish, snails, worms, and sponges
No land-dwelling plants or animals
first in Paleozoic

Answer 33

Cambrian period

Question 34

life continued to flourish during this period as it did in the earlier Cambrian period
Invertebrates, namely molluscs and arthropods, dominated the oceans.
The Great (this period name) Biodiversification Event considerably increased the diversity of life.
Fish, the world’s first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period.
Largely jawless fishes
Life had yet to diversify on land.
The end of the period was marked by the (this periods name)–Silurian extinction events.
second in Paleozoic

Answer 34

Ordovician period

Question 35

a period when vertebrate and invertebrate marine life continued to thrive
Echinoderms (relatives of sea stars) and corals more common
Eurypterids (sea scorpion like creatures)
A significant evolutionary milestone during this period was the diversification of jawed fish and bony fish.
Earliest land plants on land
Late (this periods name) scorpions evolved on land
third in Paleozoic

Answer 35

Silurian period

Question 36

known as the Age of Fishes because this was a time of major development and differentiation of fish
Significant developments in fishes
Armored fish, Jawed fish, and Lobe-finned fish
Corals and algae contribute to great reef building
On land plants continue to evolve and diversify, move from very simple things like mosses in the beginning of (this periods name) to ferns and primitive trees
By the end of the this period the first seed plants had developed
At the very end of this period the lobe-finned fishes began to crawl onto land and led to the earliest of the amphibians.
Tiktaalik
fourth in Paleozoic

Answer 36

Devonian period

Question 37

the climate was generally warm and humid.
Plants from the Devonian continued to evolve and forests/swamps began to cover much of the available land
Coal deposits we find today come from the fossilized remains of ferns and plants of this time
Amphibians and fish continued to flourish and grow during this period.
Insects became common on the land. Because of large oxygen levels with the global forests insects grew large!
Giant cockroaches and dragonflies were very common
Toward the end vertebrates began to become more adapted to life on land producing early reptiles
fifth in Paleozoic

Answer 37

Carboniferous period

Question 38

marks the end of the Paleozoic era
During this time the continents joined to form the supercontinent Pangea.
This created the Appalachian mountains
Terrestrial life in this period included diverse plants, fungi, arthropods, and various types of tetrapods.
Plant life on land shifted from fern-like groups to gymnosperms
Insects continued to thrive.
Reptiles began to flourish and differentiate
A mass extinction occurs a large number of paleozoic life forms occured at the end of this period. Known as the P-T Mass extinction.

Answer 38

Permian period

Question 39

the geologic era that lasted from 251 Mya to 65.5 Mya
Known as the Age of Reptiles
Pangea begins to break apart during this time creating smaller continents, collisions create mountains, and shallow seas/marshes cover much of the land
The climate was warm and humid
Conditions favored the survival of reptiles.
Lizards, turles, crocodiles, snakes, and a variety of dinosaurs flourished during this time.

Answer 39

Mesozoic era

Question 40

the first period of the mesozoic era
Therapsids and archosaurs were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared late in this period but did not become dominant until the succeeding Jurassic Period.
First dinosaurs developed
First mammals developed
The spermatophytes, or seed plants, came to dominate the terrestrial flora: in the northern hemisphere, conifers, ferns and bennettitales flourished. Glossopteris (a seed fern) was the dominant southern hemisphere tree during early times in this period.
With the extinction of large numbers of marine life in the end of the Permian things begin to bloom and take their place

Answer 40

Triassic period

Question 41

during this time dinosaurs became the dominant life form
Forests of conifers covered the planet
Fossil record indicates two major types of dinosaurs based on their hips:
Saurischians - “lizard-hipped”
Sauropods
Brontosaurus, Apatosaurus, Diplodocus
Theropods
Megalosaurus, Torvosaurus, and Allosaurus
Small feathered saurischians were the earliest relatives of modern birds**
Archaeopteryx
Ornithischians - “bird-hipped”
Stegosaurus
Ceratopsians
Pterosaurs (flying reptiles) were common during this time
Marine reptiles continue to inhabit this oceans feeding on fish
2nd in the Mesozoic

Answer 41

Jurassic period

Question 42

dinosaurs continue to dominate during this period until the end when another mass extinction occurs
Plant life became much more complex by this period
The earliest flowering plants, angiosperms, appeared.
Magnolias, willows, maples, oaks, and walnuts
Evolution of plants was aided by the bees
Common herbivores of this period included:
Ankylosaurus, ceratopsians, hadrosaurs
Large/ specialized carnivores
Tyrannosaurus rex, Spinosaurus, Velociraptor, ect.
Diversification of insects
Pterosaurs continue to develop
Ended with the (this period)-Tertiary mass extinction

Answer 42

Cretaceous period

Question 43

the current geologic era, which began 65.5 mya
Also known as the Age of Mammals
Dramatic changes in the climate have occured over the past 65 million years
Continental ice sheets have grown and receded
With changes in climate so have changes in species
Divided into two periods: Tertiary and Quaternary periods
Tertiary lasted from extinction of dinos to the last ice age
Quaternary is current period and began with last ice age
Primarily study these based on their epochs

Answer 43

Cenozoic era

Question 44

Paleocene Epoch
Many new mammals such as small rodents evolved
First primates evolved
Terror birds develop and will become apex predator across South America
Eocene Epoch
Many of the modern mammal families begin to appear
First horses evolve
First grasses appear
Worldwide temps drop by about 4 Celsius at the end

Oligocene Epoch
India collided with Asia
Antarctica drifts to position at south pole
Climate cools and dries
Many early mammals became extinct, others develop
Miocene Epoch
Some of the largest land mammals develop
Earliest human ancestors date back to this time
Pliocene Epoch
Mammalian predators evolve to near modern forms
Giant sloths flourished in N & S America
Bering land bridge appeared & Central america bridge
Migrations of many species
Ends with extinctions of many of the megafauna

Answer 44

Tertiary Period

Question 45

Pleistocene Epoch
Ice sheets advanced and retreated several times
Referred to as the “Ice Age”
Animals have characteristics allowing them to survive or forces to move to warmer climates
Fossils of the earliest Homo sapiens discovered
Holocene Epoch
Begins with the end of the last ice age
Melt leads to closing off of land bridges and formation of things like Great Lakes
Extinction of many ice age organisms
Humans developed agriculture

Answer 45

Quaternary Period