Earth and Space Science Q cards

When did dinosaurs go extinct

66 mya

The geologic column

An ordered arrangement of rock layers that is based on the relative ages of the rocks (oldest on the bottom)
- The type of rock the layers are made of
- The kinds of fossils the layers contain
- Fossils in upper layers resemble modern plants and animals

Using a geologic column

Scientists use geologic columns to estimate the age of rock layers that cannot be dated radiometrically
To determine age, scientists compare
- A given rock layer with a similar layer in a geologic column that contains the same fossils
- or that has the same relative position

Divisions of Geologic Time

The history of Earth is marked by major changes in:
- Earth's surface
- Climate
Types of Organisms
Geologists use these indicators to divide the geologic time scale into smaller units

Eon

The largest unit of geological time
Divided into four eons:
- The Hadean Eon (4.6 bya)
- The Archean Eon (4bya)
- The Proterozoic Eon (2.5bya)
- The Phanerozoic Eon (541mya)
The first three eons are part of a time interval commonly known as the Precambrian time
This 4 billion-year interval contains most of Earth's History

Era Definition

A unit of geologic time that includes two or more periods

Start of the Eras

After the Precambrian time, the Phanerozoic Eon was divided into smaller units of time called eras
The first era was the Paleozoic, which lasted 289 million years
- Contains lots of marine and terrestrial life form fossils

Period

A unit of geologic time that is longer than an epoch but shorter than an era
Each period is characterized by specific fossils and is usually named for the location in which the fossils were first discovered

Epochs

Where the rock record is most complete and least deformed, a detailed fossil record may allow scientists to divide periods into shorter time units called epochs

Ages

Epochs may be divided into smaller units of time called ages
Ages are defined by the occurrence of distinct fossils in the fossil record

Uniformitarianism

States that forces that shaped the Earth in the past continue to shape the Earth today (volcanoes and erosion by wind and water)

Sedimentary Rocks

Formed from sediment deposited millions of years ago
Sedimentary rocks are deposited in horizontal layers (Principle of original horizontality)
Deposited so that the oldest layer is on the bottom (Principle of superposition)

Faults and Igneous Rock Intrusions

The principle of cross-cutting relationships states that a fault or igneous intrusion is always younger than the rock it cuts across

Finding the Relative Age of Rocks using Index Fossils

Certain fossils called Index Fossils help geologists determine the Relative Age of Rocks
To be useful:
- The fossil must be widely distributed across different geographic areas
- Represent an organism that existed only briefly

Index Fossils

Fossils that are easily recognized, abundant, and widely distributed
Trilobites were a group of hard-shelled animals that evolved in shallow seas more than 500 million years ago
Became extinct at the end of the Paleozoic Era
Trilobites are useful because they were widely distributed geographically and represent an organism that existed briefly

Continental Drift Theory

Fossils from a fernlike plant, Glossopteris, found in Africa, South America, Australia, and Antarctica, couldn't have travelled across oceans
To determine the absolute age, geologists use Radiometric Dating

Precambrian History

From Earth's beginnings (4.56 bya) to the start of the Cambrian period 4 billion years later
Comprises about 88% of the geologic time scale
Most Precambrian rocks don't contain fossils, making correlating rock layers difficult
- Many are metamorphosed and deformed, extremely eroded, and hidden by overlaying strata

Earth Forms 

Scientists hypothesize that the Earth was formed as gravity pulled together dust, rock, and ice in space; gravity increased as the Earth grew and began pulling in more materials
The high velocity impacts caused the planet to melt and divide into specific layers based on density
Over several hundred million years, the crust and mantle cooled and hardened, forming rock

Earth's Atmosphere Evolution

Made up of gases similar to those released in a volcanic eruption today
- Water vapour, CO2, N, no oxygen
Torrential rains happened that slowly filled low areas, forming the ocean
- This reduced the water vapour and CO2 in the atmosphere, leaving behind a nitrogen-rich atmosphere

Earth's Evolution of Life

Primitive organisms evolved that used photosynthesis and released oxygen
Slowly, the oxygen content increased seen in the banded iron formations (Took the free oxygen out of the atmosphere)
Oxygen began to accumulate in the atmosphere about 2.5 billion years ago

How do Precambrian Rocks illustrate the law of superposition

It is carved by younger strata
Show the surface where younger strata are extensively eroded
Ex. The Grand Canyon, and in some mountain ranges

Shield

A large, relatively flat expanse of ancient metamorphic rock within the stable continental interior
Much of what we know is from ores mined from shields
The mining of iron, nickel, gold, and other metals is used for study

Precambrian Fossils

The most common are stromatolites
Remains of cyanobacteria have been found that extend the record of life back beyond 3.5 bya
Many fossils are preserved in chert hard, dense, chemical sedimentary rock
Plant fossils date from the middle Precambrian, but animal fossils date to the late Precambrian

The Setup of the Miller-Urey Experiment

Conducted in 1952 by Stanley Miller & Harold Urey of the University of Chicago
Apparatus simulated the atmospheric conditions of the early Earth

The Miller-Urey Experiment

Methane (CH4), ammonia (NH3), and hydrogen (H2) were all seated together in a 2:2:1 ration (1 part H2) inside a sterile 5L glass flask connected to a 500mL flash falh-full of water (H2O)
A continuous spark (similar to a spark plug in a car engine) was applied to the mixture of gases in the flask
Amino acids were synthesized

Interpreting Geological Features

James Hutton a Scottish geologist who lived in the 1700s, was the first to document Earth's history in terms of sea-level changes, erosion and natural features
Hutton's work is based on uniformitarianism as opposed to Catastrophism

Catastrophism

Changes to the Earth that have happened through sudden, violent and unusual events

Principles

Principle of Superposition
Principle of Original Horizontality
Principle of Original Lateral Continuity
Principle of Intrusive Relationships
Principle of Cross-Cutting Relationships
Principle of Fossil Succession

Principle of Superposition

In an undeformed sequence of sedimentary rocks, each bed is younger than the one below it and older than the ones above it
This is the basis of the relative ages of all strata and their contained fossils

Principle of Original Horizontality

Sediments usually form flat-lying deposits on Earth's surface
Sedimentary rocks are horizontal because the original sediments were horizontal

Principle of Original Lateral Continuity

Strata originally extended in all directions until they thinned to zero at their edges of deposition

Principle of Intrusive Relationships

Invading igneous rock is always younger than the rock it intrudes
This is an indicator of relative ages

Unconformities

Represent major gaps in time
They are the results of periods of erosion or non-deposition
Helps understand the age of the Earth

Angular Unconformity

Recognized by tilted or deformed sedimentary rocks below flat-lying sedimentary rocks

Disconformity

Erosion surfaces within a sequence of flat-lying sedimentary rocks

Nonconformity

Recognized by sedimentary rocks resting on an eroded surface of igneous or metamorphic rocks

Original Preservation

The actual organism is preserved in whole or in part
Uncommon fossils that require extremely stringent
- Freezing
- Arid/dry
- Oxygen-free

Altered Hard Parts

Shells, bones, cell walls
Mineral Replacements
- Pores within the organism's hard parts are filled with groundwater, and the original hard part (ie. Calcite) is replaced with something else (ie. silica)
- Ex. Petrified Wood

Recrystallization

Original hard parts are exposed to a significant change in temperature and pressure
The conditional changes cause the original material to organize into a more stable form
Ex. Aragonite (calcium carbonate) is recrystallized into calcite calcium carbonate

Moulds and Casts

A type of fossil that is not made of any original parts at all
Impressions made in rock

Trace Fossils 

Indirect fossils
Ex. Traces of warm tails, footprint and tracks, burrow

Zircon (Zirconium Silicate)

Extremely stable and resistant to change
Occurs in small amounts in granite and felsic rocks

Earth's Early Heat Sources

1. Asteroid Activity
2. Gravitational Contractions
3. Abundance of radioactive isotopes

Asteroid Activity

During the Proterozoic and Archean Eons, asteroids (silica and metal-rich rocks) were hypothesized to have been consistently hitting Earth
These impacts transferred energy in the form of heat

Gravitational Contraction

As more and more asteroids strike Earth, its overall mass starts to change, and therefore, Earth's gravitational constant changes
This increase in compressional energy resulted in excessive thermal energy

Abundance of Radioactive Isotopes

There were more radioactive isotopes during the Proterozoic and Archean Eons than there are now
Radioactive decay produces heat as a by-product

The Early Earth

Earth's asthenosphere differentiated over time into layers based on density
Iron sank; Oxygen and silicon floated up to the surface
Differentiation

Paleozoic Era

This division is known as Ancient Life
During most of the Era, warm shallow seas covered much of the planet
A major geologic event of the Paleozoic was the formation of the supercontinent of Pangaea

Cambrian "explosion"

For reasons unclear, 13 million years after the start of the Cambrian (530mya), there was tremendous diversification of marine life forms, some of which have never been reproduced
Most major animal phyla are found in the fossil record

Land (Geological) Features that First Appeared

Early plants such as ferns, mosses, and cone-bearing plants like pine-cone trees
By the end of the era, seed plants (gymnosperms) were common and began to form, creating forests
By the Devonian Period, grass began to grow on land and mountains formed during this era (the Appalachian Mountains)

Cambrian Period

541mya

Trilobites appeared

Ordovician Period

485mya

First vertebrates were jawless fish (filter feeders): The vertebrate protects the spinal cord, which carries signals from the brain throughout the body

Silurian Period

444 mya

First insects and arachnids (invertebrates like spiders and scorpions)
First jawed fish (later evolved into sharks-made of cartilage)

Devonian Period

419 mya

First vertebrates on land - amphibians
Evolved from the lobed-fin fish, which include some species of lungfish

Carboniferous Period

359 mya

First Reptiles

Permian Period

299 mya

Pangea begins to form (Appalachian Mountains; Dry climate; ice age in the southern hemisphere)
Fish and trilobites were still dominant

Mass Extinction

The mass extinction that ended the era caused most marine invertebrates, as well as amphibians, to disappear
At the end of this era, more than 90% of all ocean species and 70% of all land species died

What Catastrophic Event Caused the Mass Extinction

1. Volcanic Activity
2. Climate Change
3. Lowering of sea levels as Pangaea was forming (Convergent boundaries)

Mesozoic Era

Began 252mya after a major mass extinction, Pangea broke into smaller continents
3 periods: The climate was warm and humid
Ends with a mass extinction

Mesozoic Reptiles

Ichthyosaurs (Large marine reptiles)
Pterosaurs (Large flying reptiles)
Dinosaurs (Land dinosaurs)
Turtles
Crocodiles/Alligators
Lizards

Dinosaur Myths

All dinosaurs are the same
Everything that is big and extinct is a dinosaur
All dinosaurs lived at the same time
All dinosaurs are extinct

Triassic Period

252mya

Immediately after the Permian Mass Extinction
Lots of new areas are open for animals to live
Three general types of animals
- Holdovers from before the extinction
- New groups that lasted only a short time
- New groups that lasted a long time
Plant Life: Mosses, Scale Trees (Like Palm Trees), and Ginkgos

Two Groups of Dinosaurs

Ornithischian
- Hips were similar to modern bird hips
- Carnivorous short-necked, Herbivorous long-necked
Saurischian
- Hips were similar to reptile hips
- Herbivorous with or without grinding teeth

Earliest Dinosaurs (Triassic)

Eoraptor
Lesothsaurus
Pisanosaurus

The Jurassic Period

201 mya

Giant plant-eating dinosaurs
Vicious carnivore dinosaurs
Oceans are full of fish, squid, and sharks
Ichthyosaurs and Plesiosaurs
Pterosaurs
Birds

Jurassic Plant-Eating Dinosaurs

Many different forms
Many had armour to protect themselves, such as Triceratops and Ankylosaurs
Many very large (Larger than a Rhino/hippo)
Some were extremely large (as long as a city block): Diplodocus

Jurassic Carnivorous Dinosaurs

Many Different Forms
- All had sharp teeth, claws, and speed

Marine Dinosaurs

Most with similar shapes to dolphin or sharks
Ate fish and other marine animals
Some very large
All could swim very fast

Pterosaurs

Pterodactyls and Pterosaurs
Most had trouble "walking"
They were very good flyers
Had hollow bones
1ft to 16ft

Birds-Archaeopteryx

Not a pterosaur
Jaws and bone structures like dinosaurs
Bones are hollow, like birds
Feathers

Cretaceous Period

146mya

The last period when Dinosaurs lived
Ends with a mass extinction around 66mya
First flowering plants: Appeared at the same time as the number of insects

The Cretaceous Mass Extinction

Approximately 60% of all species went extinct
Affected more marine animals
Organisms that went extinct:
- All dinosaurs, pterosaurs, and ichthyosaurs, many terrestrial plants and Many marine animals
Organisms that survived:
- Mammals, Birds, many plants (ferns used to be the most successful), trees with flowers, small lizards, crocodiles, alligators, turtles, fish, squid, and sharks

What Caused the Extinction

Meteorite Impact Theory
- 66mya, a 10km wide meteorite struck the Earth near what is now Mexico
The impact caused shock waves, tidal waves, and sent a tremendous amount of dust into the atmosphere
As the dust re-entered the Earth's atmosphere, it would have instantly heated the atmosphere, causing tremendous forest fires
The dust could have caused the Earth's climate to cool in the long run

Meteorite Impact Evidence

Unique Quartz Evidence
- Very commonly formed under high pressure/temperature
- This quartz was only found in meteorite craters and nuclear testing sites
Iridium
- An element that is very rare in Earth rocks and very common in meteorites
- The layer of rocks above the last dinosaur bones contains 160x normal

Out-dated Hypothesis

Hay Fever: Caused by the flowering plants
Dinosaurs were so big that they crushed themselves
Mammals outcompeted the dinosaur eggs
Cosmic rays killed the dinosaurs

The Cenozoic Era

Dramatic changes in climate
As temperatures decreased during the ice ages, new species that were adapted to life in cooler climates
Mammals became the dominant life-form and underwent many changes

Tertiary Period

65 mya

Includes the time before the last ice age, and is divided into five epochs

Quaternary Periods

2.58 mya

Began with the last age, all the way to the present
Includes two epochs

Paleocene Epoch

66 mya

The fossil records indicate that there were many new mammals, such as small rodents evolved
Other mammals, including the earliest known ancestors of the horse, whales, flying squirrels, and bats, evolved during this time

Eocene Epochs

56 mya

Worldwide temperatures dropped by about 4°C at the end of the epoch

The Oligocene and Miocene Epochs

O - 34 mya

M - 23 mya

The worldwide climate became significantly cooler and drier
The modern Antarctic icecap began to form. The Mediterranean Sea dried up and refilled several times
This climate change caused many early mammals to become extinct
- Large species of deer, pigs, horses, camels, cats, and dogs flourished
Climate favoured grasses, cane-bearing, and hardwood trees
Early human ancestors appeared

The Pliocene Epoch

5.33 mya

Bears, dogs, and cats evolved in modern forms
Herbivores such as the giant ground sloth flourished
Dramatic Climate changes occurred, and the continental ice sheets began to spread
The Bering land bridges and the Central American land bridge formed, allowing various species to migrate between the continents

The Pleistocene Epoch

2.58 mya

Ice sheets in Europe and North America advanced and retreated several times
Thick-furred animals flourished more (Woolly mammoth)
Other species survived by moving to warmer regions
Fossils of the earliest modern human ancestors indicated that early humans may have been hunters

The Holocene Epoch

11,700 years ago to present

Began as the last glacial period ended
As the ice sheets melted, the sea level rose about 140m, and the coastlines took on their present shapes
Modern humans developed agriculture and began to make and use tools of bronze and iron