Geologic Time

The Geologic Column

• Geologic Column: The ordered arrangement of rock layers.

• A geologic column represents a timeline of Earth’s history. The oldest rocks are at the bottom of the column.

• Rock layers in geologic column are distinguished by the types of rock the layers are made of and by the kinds of fossils the layers contain

Units of Geologic Time Scale

• Eons: The largest geologic time. There are four eon time periods. We are in the Phanerozoic Eon now.

• Eras: There are three eras: Paleozic Era which lasted 291 million years.

• Mesozoic Era which lasted 186 million years• Cenozoic Era which began 65 million years ago

to the present.

The Geologic Column

• Periods divide Eras into smaller units of time.• Each period is characterized by specfic fossils

and is usually named for the location in which the fossils were first discovered.

• Epoch are a smaller time units of a Period• Ages are shortest time unit of an Epoch.

Precambrian Period

• 4.5 Billion years ago to 543 Million years ago• Consider that the Earth formed,• life originated, • the first tectonic plates formed and began to

move, • eukaryotic cells evolved,• the atmosphere became enriched in oxygen.• complex multicellular organisms, including the

first animals, evolved.

Precambrian

• Rodinia, the oldest supercontinent for which we have some record, formed during the middle Proterozoic (~ 1100 million years ago) with North America in the center, South America to the east, and Australia and Antarctica to the west. When the Panthalassic Ocean formed about 750 million years ago,

Precambrian Period

Cambrian Period

• 543 to 490 Million Years Ago

• The supercontinent Pannotia had begun to break up as the Iapetus Ocean formed in between Laurentia (North America),

• Fossil evidence tells us that Laurentia was centered on the Equator and rotated so that in present-day terms, Canada was east, instead of north, of the United States. As with most of the continents, the majority of North America was underwater throughout the Cambrian Period.

Cambrian Period

• "Cambrian Explosion." Animals with hard skeletons first appeared in the Cambrian and the diversity of life on Earth increased very rapidly.

• The Burgess Shale of western Canada is an exceptional site where we find fossils of many rarely preserved soft-bodied organisms.

Cambrian Period

Cambrian Questions

1. What was the time period of the Cambrian Period?

2. What was happening to the landmass on Earth?

3. What was the location of North America during the Cambrian Period?

4. What was the plant and animal life during the Cambrian Period?

Ordovician Period

• 490 to 443 Million Years Ago • From the Early to Middle Ordovician, the earth

experienced a milder climate• As Gondwana reached the South Pole during

the Late Ordovician, massive glaciers began to form, causing sea level to drop.

Ordovician Period

• During the Ordovician, Laurentia was located near the equator while it rotated about 45° counter-clockwise, closer to its present orientation. A shallow sea covered most of the continent, depositing limestones, shales, and sandstones

• Glaciation at the end of the Ordovician resulted in a drop in sea level, so some rocks deposited earlier were exposed and eroded.

Ordovician Period

• A typical marine community consisted of these animals, plus red and green algae, early fish, cephalopods, corals, crinoids, and gastropods. A drop in sea level may have contributed to the mass extinctions that characterized the end of the Ordovician, in which perhaps 60% of all marine invertebrate genera went extinct.

Ordovician Period

Ordovician Period Questions

1. What was the time span of the Ordovician Period?

2. What was the condition on Earth during the Ordovician Period

3. What was the location and condition of North American during the Ordovician Period

4. What was the plant and animal life like during Ordovician Period?

5. Why did the Ordovician Period end?

Silurian Period

• 443 to 417 Million Years Ago• The massive southern hemisphere glaciers that had

formed during the Late Ordovician began melting, and Earth’s climate became relatively stable

• A shallow sea covered much of North America during the Silurian, except for its southern margin

• In the shallow sea, limestones, shales, and sandstones were deposited, and many large reefs developed

Silurian Period

• The Silurian Period was one of the shorter periods of the geologic time scale.

• Within the Silurian rocks, we find the first coral reefs

• Jawless fishes diversified, and the first fish with jaws appeared

• We find the earliest good evidence of life on land during the Silurian Period.

Silurian Period

Silurian Period Questions

1. What was the time span of the Silurian Period?

2. What was the condition of the Earth during the Silurian Period?

3. What was location and conditions of North America during the Silurian Period?

4. What was the plant and animal life like during the Silurian Period?

Devonian Period

• 417 to 354 Million Years Ago • Most of the continental landmasses were bunched

up, and a vast ocean covered the rest of the planet. • Most of North America was covered by a shallow

sea throughout the Devonian, although some small landmasses were exposed around the continent.

• By 390 million years ago, North America and Europe collided to form a large continent, called Euramerica, which sat near the equator.

Devonian Period

• The Devonian is often referred to as “the Age of Fishes.” Many new kinds of fish appeared. Armored fish with bony plates in their mouths instead of teeth, reached their greatest diversity. Armored jawless fishes became abundant, as did early sharks and rays.

• Two major animal groups colonized the land during the Devonian. The first tetrapods (four-limbed, land-living vertebrates) appeared during the Devonian, as did the first terrestrial arthropods, including wingless insects and the earliest arachnids.

Devonian Period

Devonian Period Questions

1. What was the time span of the Devonian Period?

2. What was the condition of the Earth during the Devonian Period?

3. What was the location and condition of North America during the Devonian Period?

4. What was the plant and animal life like during the Devonian Period?

Carboniferous Period

• 354 to 290 Million Years Ago • During the Carboniferous, small oceans began to

close, bringing together the western half of Pangea

• The word “Carboniferous” comes from the Latin, meaning “coal-bearing.”

• During the Early Carboniferous limestones, shales, sandstones, and evaporites were deposited in the shallow sea that covered most of North America.

Carboniferous Period

• Late Carboniferous, when North America started to collide with Gondwana. The collision uplifted the ancestral Rocky Mountains, the Ouachita Mountains of Oklahoma, the Appalachians, and much of present-day eastern Canada and the East Coast from Maine to Alabama

• Vast swamps formed over low-lying areas of North America, Northern Europe, and Asia during the Late Carboniferous. The lush vegetation of these swamps became coal.

• One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed the ancestors of birds, mammals, and reptiles to reproduce on land

Carboniferous Period

Carboniferous Period Questions1. What was the time span of the

Carboniferous Period?2. What was the condition of Earth

during the Carboniferous Period?3. What was the location and condition

of North America during the Carboniferous Period?

4. What was the plant and animal life like during the Carboniferous Period?

Permian Period

• Permian Period from 290 to 248 Millions of years ago.

• Around the world, the continental collisions begun in the Carboniferous continued into the Permian.

• The formation of Pangea closed smaller seas between continents and upliftedmountain ranges around the supercontinent

Permian Period

• During the Permian Period there was a large continental interior which generated a dry climate with great seasonal fluctuations.

• As Pangea was assembled, most of North America was being uplifted during the Permian. This uplift generated the famous fold belts of the Appalachian Mountains

• Shallow seas covered much of modern western North America. Large reef complexes developed

Permian Period

• The Permian Period marks the end of the Paleozoic Era and the time of the largest mass extinction in Earth’s history.

• It has been estimated that nearly 90% of all species became extinct at the end of the Permian.

• As the climate became drier, the vast swamps of the Carboniferous disappeared and were replaced by forests more tolerant of dry conditions. Modern conifers first appeared in the fossil record of the Permian.

Permian Period

Permian Period Questions

1. What was the time span of the Permian Period?

2. What was the condition of the Earth during the Permian Period?

3. What was the location and conditions of North America during the Permian Period?

4. What was the condition of the plants and animals during the Permian Period?

5. What happen to most of the animals at the end of the Permian Period? Why?

Triassic Period

• The Triassic Period - 248 to 206 Million Years Ago.

• Western Pangea had already assembled, and Eastern Pangea began to assemble.

• By the latest Triassic, just as the formation of Pangea was complete, the supercontinent began to break up, and rifts developed between North America, Africa, and South America

Triassic Period

• There was an arid climate and resulted in large seasonal temperature variations over most of the supercontinent throughout the Triassic.

• As Pangea began to break apart, rift basins developed along the modern East Coast and filled with sediment and lava flows.

• During the rifting, regions that once were part of Africa remained attached to North America, including parts of the Atlantic Coastal Plain and most of Florida

Triassic Period

• Shallow seas covered most of the continent west of the modern Rocky Mountains and north into Canada.

• The Triassic Period was a time of transition as life on Earth was recovering from the great mass extinction that ended the Paleozoic Era

• The dinosaurs made their first appearance in the Triassic, and diversified to dominate the terrestrial faunas for the next 180 million years.

Triassic Period

• The Triassic seas were home to other large reptiles.

• The earliest flying vertebrates, the pterosaurs, evolved during the late Triassic.

• One other vertebrate group evolved in the Triassic at about the same time as the dinosaurs: the mammals.

Triassic Period

Triassic Period Questions

1. What was the time span of the Triassic Period?

2. What was the condition of the Earth during the Triassic Period?

3. What was the location and condition of North America during the Triassic Period?

4. What was the condition of the plants and animals during the Triassic Period?

Jurassic Period

• The Jurassic Period - 206 to 144 Million Years Ago.

• In the Early Jurassic, Pangea was breaking up between modern North America, Africa, and South America.

• At the same time, volcanic activity began along adjacent margins of East Africa, Antarctica, and Madagascar, where the South Atlantic Ocean would later form

Jurassic Period

• Global climate during the Jurassic was relatively warm and moist over much of northern North America, Eurasia, and Indo-Australian

• Desert and seasonally wet conditions were present throughout much of Africa, South America and southern North America.

• As Pangea rifted apart, North America moved northwest during the Jurassic Period

Jurassic Period

• The shallow seas that covered the interior of North America retreated to the western edge of the continent.

• Subduction on the western edge of the continent caused frequent volcanic eruptions, forming the igneous rocks in the core of the region.

Jurassic Period

Jurassic Period Questions

1. What was the time span of the Jurassic Period?

2. What was the condition of the Earth during the Jurassic Period?

3. What was the Location and condition of North America during the Jurassic Period?

4. What was the plant and animal life like during the Jurassic Period?

Jurassic Period

• Dinosaurs diversified to fill most of the major ecological nichesfor land animals. Jurassic dinosaurs reached tremendous sizes

• Ammonites, coiled and straight-shelled relatives of the modern chambered Nautilus, were major predators among the invertebrate

The Cretaceous Period

• The Cretaceous - 144 to 65 million years ago• he second major episode of continental rifting

in the breakup of Pangea began in the Early Cretaceous. South America and Africa separated slowly from south to north creating the South Atlantic Ocean.

• Throughout the Cretaceous, sea level was an average of 100 meters higher than today due to continental rifting and sea-floor spreading.

Cretaceous Period

• Shallow seaways spread over many of the continents, including North America, South America, Africa, and Eurasia.

• Climate was globally warm during the Cretaceous, partly due to the mediating climatic effects of the shallow seas, and partly because the continental positions allowed warm waters to circulate around the globe.

Cretaceous Period

• During the Cretaceous, North America was moving northwest, closer to its present position.

• A large inland sea spread over much of central and southern North America.

• Low mountains stood out along the modern Appalachian Mountains and lowlands dominated from the modern Great Lake States into eastern Canada.

Cretaceous Period

• Subduction along the western continental margin accelerated, adding intrusive and extrusive igneous rocks to the ancestral Sierra Nevada.

• The ancestral Rocky Mountains were uplifted, and exotic terranes were being added to its western margin.

Cretaceous Period

• The Cretaceous Period may be best known for its ending. Marking the boundary between the Mesozoic and Cenozoic Eras.

• The end of the Cretaceous is defined by one of the most famous mass extinctions in the history of life on Earth.

• It has been estimated that perhaps 60-70% of all marine species and nearly 15% of all land animals.

Cretaceous Period

• It has been estimated that perhaps 60-70% of all marine species and nearly 15% of all land animals.

• the most famous victims were the dinosaurs — only their descendents, the birds, survived.

Cretaceous Period

Cretaceous Period Questions

1. What was the time span of the Cretaceous Period?

2. What was the conditions on Earth during the Cretaceous Period?

3. What was the location and condition of North America during the Cretaceous Period?

4. What were the plants and animals like during the Cretaceous Period?

5. What caused the Cretaceous Period to end? Why?