Module 7 Geological Time and Human Population. Origin of Earth When the solar system formed, gas and dust (called a nebula) 15 billion miles across accumulated.

Module 7

Geological Time and Human Population

Origin of Earth

When the solar system formed, gas and dust (called a nebula) 15 billion miles across accumulated in space where we are now

99.9% of the accumulation went to make the Sun

Photo: NASA Hubble

The Earth formed 4.55 BILLION years ago.

This is called DEEP time because it is hard for humans to imagine that kind of time span.

The early Earth was a hot and molten place with no atmosphere.

Photo: NASA

Around the same time, an asteroid as big as Mars hit the Earth and gauged out a chunk that became our moon. It was big enough to establish an orbit.

Image: NASA

Geologic Time (Deep Time) - Earth’s history includes 4.55 billion years. In order to divide geologic time into workable units, scientists have established the geologic time scale, which is divided into four geologic eras:

Photo Credit: Carthage.org

Precambrian Era – 4 billion years long (87% of Earth’s history). Most important events in biological history took place.

At Earth’s start there was molten rock, atmosphere full of poisonous gases, widespread volcanic eruptions.

Life’s Origin – 3.5 billion years ago

Earth is cooler, continents and oceans have formed, the air is warm and has little oxygen, lightening is constant and rain falls continually.

Image: NOAA

• In this environment, life began to form.• From small organic molecules, simple cells (cyanobacteria) developed in the sea. •This took millions of years.• These organisms could photosynthesize, putting oxygen into the atmosphere.

Image Creidt: Sercblog.si.edu

By the end of the Precambrian, oxygen has built up in the atmosphere, and simple multicellular life forms (sponges, jellyfish, corals, worms and clams) have developed and tectonic plates have begun to move.

Image; NOAA

Paleozoic Era – 345 million years long, “Age of Ancient Life”; Bracketed by two of the most important events in the history of animal life.

Begins with dramatic explosion in diversity of multicellular animals. Almost all living animal phyla appeared within a few million years.

The evolution of hard parts such as bones and shells in animals led to abundant fossils. From these fossils, scientists theorize that marine invertebrates were common at the beginning of the era, next came vertebrates (fish), followed by amphibians and then reptiles. Insects also evolved during this period.

Image: NSF

Plants evolved and became common – expanding into terrestrial environments 400 million years ago (mya). Our fossil fuels (coal, oil, natural gas) came from the remains of dense forests of club moss, horsetails, and ferns that were common 300 mya.

Image: USGS

The six Paleozoic continents experienced tremendous mountain building along their margins, and numerous beginnings and retreats of shallow seas in their interior (these created large limestone outcrops, which are used for building and industry).

Image: USGS

The Paleozoic ended when all of the continents on Earth drifted together forming a large continent called Pangaea, and the largest mass extinction in history wiped out approximately 90% of all marine animal species.

Image: USGS

Mesozoic Era – 160 million years long, “Middle Animals” This is the time that the world flora (plant life) and fauna (animal life) changed dramatically.

Image: news.science360.gov

Triassic Period – first dinosaurs and first mammals appear in the fossil record. Mammals remained small and insignificant while the dinosaurs were dominant. Modern fish and insect types develop, and modern gymnosperms, such as conifers, first appear.

Image: NSF

Jurassic – The Rocky Mountains rise and the volcanoes of North America West are active. The first birds appear, primitive mammals continue to develop, and the largest dinosaurs thrive. Palms and cone-bearing trees flourish.

Image: NSF

Cenozoic Era – 65 million years, and counting (includes present time)

Tertiary Period (from 65 millions years ago to 1.8 million years ago) – Andes, Alps, and Himilayan Mountains rise. The first horses, primates, and human-like creatures (hominids) develop, mammals take on present-day features, and flowering plants thrive.

• Quaternary Period (from 1.8 mya to now) • Ice covers large parts of North America and

Europe.• The Great Lakes form as ice melts. • The first modern human beings appear, and

civilization begins. • Human recorded history is less than 5,000

years old.

Image: USGS

Trends in Geologic Time

Each era can be divided into periods. Each period can be divided into

epochs. Each of these units is characterized

by different environmental conditions and specific kinds of life that flourished

How do we know?

•Scientists use records preserved in rock (fossils) to support divisions of time.

•Radiometric Dating—This allow scientists to chemically prove how old rocks and fossils are.

•Often, the boundaries between geologic time periods were marked by mass extinctions.

Geologic History of North Carolina

• North Carolina represents more than a billion years of constant change.

• Some events in a timeline of NC Geology (in millions of years ago):

1. 1800 mya – oldest dated rock in NC. Found on Roan Mountain.

2. 1200- 1000 mya – Greenville orogeny (process of mountain building)

•750 – 550 mya – Oldest known fossil in NC (620 mya); Formation of Mr. Rogers and Grandfather Mountain Formations

•550 – 475 mya – Emplacement of granite (in Chapel Hill, Roxboro, and Vance County); gold deposits form

•475 – 400 mya – Initial formation of Brevard, Hayesville, and Greenbriar thrust faults; Collision between North America and a volcanic island arc (future Piedmont).

•380 – 350 mya – Emplacement of granite (Mount Airy, Concord, and Salisbury)

•300 – 240 mya – Emplacement of granite in the Piedmont, Final assembly of supercontinent Pangae as Africa and North America collide

•200 – 180 mya – Clay and coal deposited in rift basins; Dinosaur, reptile, and other fossils and footprints made; Initial opening of Atlantic Ocean

• 130 mya – Cape Fear Arch begins to develop

•100 – 65 mya – Major rise in sea level; Dinosaur bones and teeth, shark’s teeth and shells

•50 – 25 mya – Abundant marine fossils, including whales

•25 mya – Rapid cooling of Atlantic Ocean

•10 mya – Tectonic uplift and subsequent erosion of Mountains and Piedmont.

• 9 – 3 mya – Gulf Stream established

•2.8 mya to now – Formation of peat deposits and Carolina bays; Ice Ages: climate alternated between cooler/wetter and warmer/drier than present; Formation of modern floodplains

Current research can redefine the placement of these events. •For example, Dr. Stanley Riggs of ECU has recently discovered that the Outer Banks have experienced numerous disappearances and reformations within the last 12,000 years using seismographs and sediment core analysis (combined with radiometric dating of the cores)

Although much remains to be learned, a general understanding of the regional geologic relationships has emerged. The state can be described in terms of geologic belts – areas with similar rock types and geologic history.

Image: NCSU

Human Population

• By studying geological time we can see that humans have been on the Earth for a blink of an eye.

• Yet, we have taken control of the Earth and our population is now 7 billion.

• Humans need Earth’s resources to survive.

• We need fresh clean water.• We need clean air to breathe.• We need the food that begins with

plants.

As our population grows, some scientists wonder if the Earth will be able to provide all the needs of a growing human population.

This is why it is crucial to protect Earth’s resources.

•Soils for growing crops•Clean water for good health•Clean air to breathe•Energy needs; electricity, gasoline, industry, etc