Transcript Periods period

18.1 The Geologic Time Scale
Essential Question: summarize the
development of the geologic
column and its Major units of time
Homework:
5/8 vocabulary page 360 – define and give one fact
5/6 section review page 346
18.1 The Geologic Time Scale
geologic column 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.
► Evidence
of changing conditions on Earth’s surface
is recorded in the rock layers of Earth’s crust.
► The
geologic time scale outlines the development
of Earth and of life on Earth.
The Geologic Column
►Rock layers in a geologic column are distinguished
by the types of rock the layers are made of and by
the kinds of fossils the layers contain.
►Fossils in the upper layers resemble modern plants
and animals.
►Many of the fossils discovered in old layers are
from species that have been extinct for millions of
years.
Divisions of Geologic Time
►The geologic history of Earth is marked by major
changes in Earth’s surface, climate, and types of
organisms.
►Geologists use these indicators to divide the
geologic time scale into smaller units.
►Rocks grouped within each unit contain similar
fossils and each unit is generally characterized by
fossils of a dominant life-form.
Earth-History Clock
► Eon
 Era
►Period
 Epoch
Eons
►The largest unit of geologic time is an eon.
Geologic time is divided into four eons: the
Hadean eon, the Archean eon, the
Proterozoic eon, and the Phanerozoic eon.
►the Hadean eon, the Archean eon, the
Proterozoic eon = Precambrian Time. This 4
billion year interval contains most of Earth’s
history.
Eras
era a unit of geologic time that divides eons
into smaller units of time.
►Only the Phanerozoic eon is divided into
eras.
►Examples: Paleozoic, Mesozoic, and
Cenozoic eras
Periods
period a unit of geologic time that divides
eras into smaller units of time.
►Eras are divided into shorter time units
called periods. Each period is characterized
by specific fossils.
►Example periods: Devonian, Jurassic,
Quaternary periods.
Epochs
epoch a subdivision of geologic time that
divides periods into smaller units of time.
►Where the rock record is most complete, a
detailed fossil record may allow scientists to
divide periods into shorter time units called
epochs.
►Examples: Paleocene, Pleistocene, Holocene
epochs.
18.2 Geologic History
Essential Question: Identify the
Characteristics of Precambrian Rock and
what has been learned of life in the
Paleozoic era, Mesozoic era and Cenozoic
era
Evolution
evolution an inheritable change in the
characteristics within a population from one
generation to the next; the development of new
types of organisms from preexisting types of
organisms over time.
►By examining rock layers and fossils, scientists
have discovered evidence that species of living
things have changed over time.
►Scientists call this process evolution.
Evolution and Geologic Change
►Scientists think that evolution occurs by means of
natural selection. Evidence for evolution included
the similarity in skeletal structures of animals.
►Major geologic and climatic changes can affect the
ability of some organisms to survive.
►By using geologic evidence, scientists try to
determine how environmental changes affected
organisms in the past.
Evolution
Precambrian Rocks
► Precambrian
time is from 4.6 billion years ago
to about 540 million years ago, stared when
the Earth’s crust cooled enough for rocks to
form.
► The rock material has been completely changed
by the process of plate tectonics and
metamorphism
► Exposed Precambrian rock is call a shield and
can be found on every continent, half of all
valuable minerals are here. (gold, iron, nickel,
and copper)
Precambrian Rocks
► Fossil
are a rare find, the most common is a
Stromatolites, which formed from cynobateria
► This implies shallow seas, the imprints of
worms, jellyfish, and one celled organisms have
been found late in Precambrian rocks
The Paleozoic Era
► Started
540 million years ago and ended
248 million years ago
► The continents came together during this
time and there was abundant life in the
oceans and on land
► This era has been divided into seven
periods: Cambrian, Ordovician, Silurian,
Devonian, Carboniferous and Permian
The Cambrian period
► During
this period there was an explosion of
marine life, trilobites been one of there marker
index fossils used to date the different periods.
► Brachiopods also formed during this time and
still exist today
► The fossil record is rich because animals
developed hard shells during this period.
► There is no evidence of life on land in this
period
The Ordovician Period
► More
brachiopods developed and the
trilobites began to decline, snail clams and
other mollusk became the dominate life
forms
► The first fish with a vertebrate developed in
this period, no jaws or teeth and it had
bony plates
► Still no life on land
The Silurian Period
► During
this time both invertebrate and
vertebrate creatures thrived
► Echinoderms (sea stars) and corals became
more numerous, as well as eurypterids ( a
scorpion like creature) that reach 2.7 m in
length.
► Early plant life formed and spiders and
millipedes evolved
The Devonian Period
► This
is the age of fish, a population
explosion of fish caused adaptations like air
breathing fish or lung fish
► Amphibians probably evolved from these
fish
► Land plants, giant horsetails, ferns and cone
bearing plants
The Carboniferous Period
► This
is the period, it is believed, that coal
and oil formed
► It is also a time when it was warmer and
more humid world wide, swamps and forest
covered most of the land
► Insects dominated the land and at the end
of the period the first lizards evolved
The Permian Period
► Was
the first mass extinction, many marine
life disappeared forever
► The land joined together to form Pangaea
► Reptiles flourished in this new environment
The Mesozoic Era
► 248
million years ago to 65 million years ago
► The planet was warm and humid
► Pangaea broke apart, tectonic plates collide
and formed new mountain ranges
► Reptiles like lizards, turtles, crocodiles, snakes
and dinosaurs … the age of reptiles
► Broken into three periods; Triassic, Jurassic,
and cretaceous
The Triassic Period
► Dinosaurs
first appeared, some as small as a
squirrel and others up to 30 m
► most about 4 to 5 meters, could move quickly
► The land was covered with cone bearing trees
and palms
► The even inhabited the oceans
► Mammals first appeared in the forest and
about the size of a rodent
The Jurassic Period
► Dinosaurs
dominated, two types saurischians
(lizard hip) and ornithischians (bird hip)
► Lizard hip included herbivores and carnivores,
the largest was Apatosaurus at 25 meters and
50 tons
► The stegosaurs was part of the bird hip
► Pterosaurs was a flying dinosaur and the first
feather bird appeared at this time.
The Cretaceous Period
► Dinosaurs
still ruled the world with a great
variety of creatures and T-Rex as the apex
predator
► Plant life also evolved into angiosperm,
which means they flower and fruit
► A mass extinction ended this period, no
dinosaur fossils found after this period
Mass Extinctions
The Cenozoic Era
► 65
million years ago to the present
► Continents close to current positions, tectonic
activity increased forming the Alps and
Himalayas
► Major climate change, mammals become
dominate life on the planet.
► Two periods; tertiary and quaternary
► Seven epochs; paleocene, eocene, oligocene,
miocene, pliocene (tertiary), pleistocene and
holocene (quaternary)
Paleocene and Eocene
► Mammal
evolution took off
► The first primates evolved, lemurs
► The worldwide temperature dropped 4
degrees celsius
Oligocene and Miocene
► The
large mammals developed in this time
as the planet grows colder
► Sea levels dropped and the polar ice caps
formed
► Deer, horses, camels, cats, dogs, raccoons,
wolves, pigs and saber tooth cat
Pliocene
► Fully
evolved dogs, cats, bears and horse
appeared in this epoch
► The ice age started and land bridges
between the continents formed allowing the
animals to travel
Pleistocene and Holocene
► There
where several ice ages in this time, with
some animals developing thick fur or migrating
to warmer climates and some went extinct
altogether
► Humans first appeared as hunters
► The Holocene started 11,000 years ago with
the end of the ice age, Homo sapiens
developed agriculture and use tools made from
metals