Welcome toESC 102Evolution of Earth and Life

HistoricalGeology

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

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.

UniformitarianismThe 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

Slide 12 Fig 1-9, p. 12

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 2.7o 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

Evidence of the Big Bang

• Galaxies moving away – expanding universe(proposed by Hubble)

Imagine the surfaceof a balloon as itis inflated. Locations on the surface move away from one anotherThe further away objects are, the faster they are moving away = acceleration.

EB

C

AE

B

C A

Doppler effect

• https://www.youtube.com/watch?v=h4OnBYrbCjY

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.

• 1993Age: 12-20 Billion YearsSize: 30 Billion Light Years 2006

Age: 13.7 Billion YearsSize: 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

• condensed and collapsed due to gravity

• forming solar nebula – with an embryonic Sun – surrounded by a rotating cloud

• cloud of gases and dustformed 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 distinctorbits 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.

Solar Nebula Theory

The PlanetsTerrestrial

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

Relative Sizes of the Sun and Planets

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 HistoryDifferentiation = segregated into layers

of differing composition and density

Early Earth was probably uniformAfter heating, molten iron and nickel sank to form the coreLighter 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 hypothesisForming the Moon

Slide 8 Fig 1-5, p. 9

Most of the lunar materialcame 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

OxygenSilicon

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

Geologic TimeHuman perspective

seconds, hours, days, years

Ancient human history

hundreds or even thousands of years

Geologic history

millions, hundreds of millions, billions of years

UniformitarianismThe Present is the key to the

pastTHE UNIFYING PRINCIPLE

OF

GEOLOGY

Present day mud cracksAncient mud cracks