Evolution of Earth and Life ESC 102 Evolution of Earth and Life Historical Geology Spring 2011 This is ESC 102 Evolution of Earth and Life

Earth Systems can you identify them? When we view the Earth from space what Earth systems are observable? What is most obvious? Are these systems independent or do they interact with one another? What is the first thing you notice when you view the Earth from space?

Systems = Spheres of the Earth 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’s spheres definitely interact. Give an example of the interaction of two or more spheres.

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.

Something Happened….. James Hutton observed tilted sedimentary layers overlain by near-horizontal layers. He realized that whatever processes created this rock outcrop must have taken millions of years. In 1785, published his Theory of the Earth and is considered founder of modern geology.

Charles Lyell wrote “Principles of Geology in 1830. He furthered the work of James Hutton: concept of Uniformitarianism Rock layers reveal sequences of events based on processes that occur today.

Historical Geology applies geologic principles to help predict and explain Earth’s materials William Smith was an English surveyor who realized that rock types and fossils occur in repeated patterns. He was able to predict rock sequences that would be encountered in constructing canals Smith mapped the geology of much of England. (1815)

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

Hypothesis or Theory? The scientific method brings an orderly and logical approach to decoding geologic evidence. A hypothesis is a tentative explanation for observations Scientists make predictions using hypotheses – then they are tested After repeated testing, a theory may be proposed Some phenomena cannot be tested or explained

A theory is formed A theory is more than an “educated guess” A theory explains natural phenomena and may relate several observations A theory is well-tested and well-supported by objective evidence Examples include: Plate Tectonics Theory Theory of Organic Evolution

Where do scientists look for evidence for the following? The origin and age of the universe The origin and age of the solar system The origin and age of the Earth and Moon The origin of life on Earth Evidence of plate movement on Earth Explanation for large scale extinctions on Earth

How old is the universe? When? Scientists believe the universe was formed about 15 billion years ago 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 2.7o C above absolute zero is observed in space (-273o C or -460o F) “Afterglow” of the Big Bang discovered in 1965 As predicted, it was cosmic microwave radiation from .space Fahrenheit absolue zero ~ 460 degrees Glow was predicted and discovered in 1965 by Penzias and Wilson (nobel prize)

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.ther.

Evidence of the Big Bang Determine the Age of the Universe Determine rate of expansion “Back-model” to a time when the galaxies would be together in the same space

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.

Enormous expansion occurred 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 and weak nuclear forces Enormous expansion occurred

Big Bang Model 300,000 years later: Next 200 million years: 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 fusiion

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

Origin of Our Solar System Solar nebula theory cloud of gases and dust formed a rotating disk condensed and collapsed due to gravity forming solar nebula with an embryonic Sun surrounded by a rotating cloud

Embryonic Sun and Rotating Cloud Planetesimals have formed in the inner solar system, and large eddies of gas and dust remain far from the protosun

The planets formed with distinct orbits around the sun 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 shows a solar nebula as a protoplanetary disk or “proplyd” located in Orion Nebula with dozens of others. The proto star is the bright glow; dark area is a dense molecular cloud. This image from the Hubble Space Telescope shows a solar nebula, evidence to support the Solar Nebula theory. This is called a protoplanetary disk, or proplyd. This proplyd lies at the heart of the Orion Nebula along with dozens of other proplyds. The darker area is the dense molecular cloud while the proto-star (a star that is hot, but not hot enough to initiate fusion) is the glow in the center.

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

The Planets Terrestrial Planets Jovian 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 probably with uniform composition/density Temperature increased. Heat sources were: meteorite impacts gravitational compression radioactive decay Heated up enough to melt iron and nickel within the newly formed Earth

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

Earth’s Differentiation 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 for moon

Most of the lunar material came from the mantle of the colliding planetesimal The material cooled and crystallized into lunar layers Moon is smaller than Earth and cooled quickly. Light colored surface areas are lunar Highlands – heavily cratered. evidence of 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: Oxygen Silicon aluminum

Earth’s Interior Layers Lithosphere solid upper mantle and crust -- broken into plates that move over the asthenosphere Asthenosphere part of upper mantle behaves plastically and slowly flows

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

Plate Tectonic Theory Movement at plate boundaries At plate boundaries plates diverge plates converge plates slide sideways past each other At plate boundaries Volcanic activity occurs Earthquakes occur

Modern Plate Map Active tectonic boundaries are in red

Plate Tectonic Theory After decades of puzzling evidence, the theory was developed in the1960s Provides a framework for interpreting many aspects of Earth on a global scale and relating many seemingly unrelated phenomena Key to interpreting Earth history The “unifying theory of geology”

Plate Tectonics and Earth Systems Mechanism: Plate tectonics is driven by convection in the mantle and in turn drives mountain building and associated igneous and metamorphic activity Global effects of plate movement: Arrangement of continents affects solar heating and cooling, winds and weather systems Rapid plate spreading and hot-spot activity may release volcanic carbon dioxide and affect global climate

History of Earth The history of the early earth through the present is revealed mainly in the rock and fossil records. By applying principles of formation and determining environments from life forms, early interpretations about Earth’s land masses and oceans have been made

Theory of Organic Evolution Provides a framework for understanding the history of life Darwin’s On the Origin of Species by Means of Natural Selection, published in 1859, revolutionized biology Provided the mechanism of natural selection

Central Thesis of Evolution All present-day organisms are related and descended from organisms that lived during the past Natural selection is the mechanism that accounts for evolution Natural selection results in the survival to reproductive age of those organisms best adapted to their environment

History of Life The fossil record provides perhaps the most compelling evidence in favor of evolution Fossils are the remains or traces of once-living organisms Fossils demonstrate that Earth has a history of life

Geologic Time From the human perspective time units are in seconds, hours, days, years Ancient human history hundreds or even thousands of years Geologic history millions, hundreds of millions, billions of years

Geologic Time Scale Resulted from the work of many 19th century geologists who pieced together information from numerous rock exposures, constructed a sequential chronology based on changes in Earth’s biota through time The time scale was subsequently dated in years using radiometric dating techniques

Uniformitarianism: The Present is the key to the past Uniformitarianism is a cornerstone of geology is based on the premise that present-day processes have operated throughout geologic time The physical and chemical laws of nature have remained the same through time