Welcome to ESC 102 Evolution of Earth and Life Historical Geology Fall 2014

Lithosphere: Earth’s solid rocky mass Hydrosphere: All of earth’s water Atmosphere: The thin gaseous layer above Earth’s surface Biosphere: All of earth’s life forms Earth Systems

Text: atmosphere, biosphere, hydrosphere, lithosphere, mantle, core The solid portions are sometimes collectively referred to as “geosphere”

Three Themes tell the story of the evolving Earth  The Theory of Plate Tectonics Solid Earth is composed of plates that move over Earth’s surface.  The Theory of Organic Evolution Earth’s biota – all living things – has evolved or changed through history.  The Geologic Time Scale Geologic processes take place within extensive geologic time -~ 4.6 billion years of Earth’s history.

Uniformitarianism The physical, chemical, and biologic processes that occur today must have occurred in the past. Rock layers reveal sequences of events based on processes that occur today.

Smith’s map took many years to complete and helped establish the geologic time scale. Geologic Time

Geologic Periods were determined by the rock record and the fossils contained in distinct layers. (1841) Numerical dates millions of years before the present have been determined by using radioactive isotope decay. (1913) Geologic Time

Hypothesis or Theory? The scientific method brings an orderly and logical approach to decoding geologic evidence A hypothesis is a tentative explanation for observations A theory is well-tested and well-supported by objective evidence 1/29

How old is the universe? When? Scientists believe the universe was formed about 15 billion years ago 13.7 billion years ago (text: 14by) How? The Big Bang is a model for the “beginning” of the universe “Show me”! What is the evidence?

Evidence of the Big Bang Pervasive background radiation of 2.7 o C above absolute zero is observed in space (-273 o C or -460 o F) “ Afterglow” of the Big Bang discovered in 1965 As predicted, it was cosmic microwave radiation from space

Evidence of the Big Bang Galaxies moving away – expanding universe (proposed by Hubble) Imagine the surface of a balloon as it is inflated. Locations on the surface move away from one another The further away objects are, the faster they are moving away = acceleration.

E B C A E B C A

Doppler effect nBYrbCjY

Evidence of the Big Bang To determine the Age of the Universe Determine rate of expansion: look at the most distant objects “Back-model” to a time when the galaxies would be together in the same space

How far can we “see” into space?

Big Bang Model Research A 7 year satellite observation project mapped the cosmic microwaves in space –Revealed the nature of many components that had been predicted in various models. The WMAP project since 2002 has enabled scientists to refine the age of the universe to 13.7 billion years and the “shape” of its surfaces Age: Billion Years Size: 30 Billion Light Years 2006 Age: 13.7 Billion Years Size: 94 Billion Light Years

Big Bang model Initial state: NO time, NO matter, NO space –Universe was pure ENERGY During the FIRST second of time: --very dense matter came into existence --The four basic forces separated: gravity electromagnetic force strong nuclear force weak nuclear force Enormous expansion occurred

Big Bang Model 300,000 earth years later: –Atoms of hydrogen and helium formed –Light (photons) burst forth for the first time Next 200 million years: –Continued expansion –Stars and galaxies began to form –Elements heavier than hydrogen and helium began to form within stars by nuclear fusion

The WMAP data indicate our universe is 13.7 billion years old, and made up of only only four percent ordinary atoms. Dark matter makes up about 23 percent. The remaining 73 percent is the enigmatic "dark energy."

9 billion years later….. The formation of the solar system

forming solar nebula –with an embryonic Sun –surrounded by a rotating cloud cloud of gases and dust formed a rotating disk Solar nebula theory Solar Nebula Theory

Planetesimals have formed –in the inner solar system, –and large eddies of gas and dust –remain far from the protosun Solar Nebula Theory

________ Solar Nebula Theory Requires Cosmic Dust Aggregation

The planets formed with distinct orbits around the sun. Some planets have satellites which orbit individual planets.

Solar Nebula Theory Is there Evidence? The Hubble Telescope image : solar nebula protoplanetary disk “proplyd” in Orion Nebula with dozens of others. The proto star is the bright glow; dark area is a dense molecular cloud.

NASA image clearly shows that this star has 4 distinct rings. These rings will eventually coalesce into solid bodies called planets.star Solar Nebula Theory

The Planets Terrestrial Planets  Mercury  Venus  Earth  Mars  Small in size  Composed of rock  Metallic cores  Asteroid Belt Jovian Planets  Jupiter  Saturn  Uranus  Neptune  Large in size.  Composed of hydrogen, helium, ammonia, methane  Small rocky cores  Kuiper Belt Pluto: no longer has planet status

Earth’s Very Early History  Started out cool about 4.6 billion years ago -- with uniform composition  Heated up enough to melt iron and nickel within the newly formed Earth –Heat sources: gravitational compression radioactive decay meteorite impacts

The earth and moon were heavily bombarded in Earth’s early history. Earth’s Very Early History

Earth’s Differentiation: Key event in Earth History  Differentiation = segregated into layers of differing composition and density  Early Earth was probably uniform  After heating, molten iron and nickel sank to form the core  Lighter minerals flowed up to form mantle and crust

Forming the Moon Impact by Mars- sized planetesimal with early Earth 4.6 to 4.4 billion years ago Ejected a large quantity of hot material that cooled and coalesced to form the moon

Impact hypothesis Forming the Moon

Most of the lunar material came from the mantle of the colliding planetessimal Moon is smaller & cooled quickly. Heavily cratered (light areas) --massive meteorite bombardment Mare areas of lava flows more likely due to impact than tectonics

Earth—Dynamic Planet  Earth was also subjected  to the same meteorite barrage  that pock-marked the Moon  Why isn’t Earth’s surface also densely cratered?

Major elements on Earth Top 4 most abundant elements by Oxygen Silicon aluminum Hydrogen Earth—Dynamic Planet

Earth’s Interior Layers Compositionally: 3 layers Crust Mantle Core Earth—Dynamic Planet

Plate Tectonics Theory Lithosphere is broken into individual pieces called plates Plates move over the weak layer –as a result of underlying convection cells

Plate Tectonics Theory

Theory of Organic Evolution  Provides a framework for understanding the history of life  Provides the mechanism of natural selection

Theory of Organic Evolution  All present-day organisms are descended from organisms that lived during the past  Natural selection results in the survival to reproductive age of those best adapted to their environment

Theory of Organic Evolution The fossil record: the most compelling evidence in favor of evolution Fossils demonstrate that Earth has a specific history of life Modern Chromosome Theory: fills in the blanks by studying the genetic makeup of any organism that can provide DNA

Uniformitarianism The Present is the key to the past THE UNIFYING PRINCIPLE OF GEOLOGY