Introduction to Earth Science What is geology Geology

Introduction to Earth Science

What is geology? • Geology (geoscience): the study of the Earth • Materials of Earth • Large scale internal processes and structures • Surficial processes sculpting the planet

Why study Geology? 1. Understand the world around us: • Why do mountains form? • How are the rocks deposited? • Where can we locate resources?

Why study Geology? 2. Understand geologic hazards • Earthquakes • Volcanoes • Floods 3. Understand natural resources • Ground Water • Coal Mining • Petroleum resources

Why study Geology? • We depend on the Earth for energy resources and raw materials • Every manufactured object relies on Earth’s resources from pencils to skyscrapers • Geology drives the world economy • Petroleum, coal, uranium, metals, gemstones, sand gravel

Why Study Geology? • Employment – diverse disciplines • • Energy industry Mining industry Water resources Construction/engineering Environmental Conservation Government (USGS) Academics

Average salary by degree (AAPG, 2010) • Careers in the geosciences routinely rank in the top five in financial magazine of job satisfaction

The Scientific Process

What is Science? ? ? • Bases on facts or observations about nature –not beliefs • Can be predictive • Falsifiable (testable)

The nature of scientific inquiry • Science assumes the natural world is consistent and predictable • Goal of science is to discover patterns in nature and use the knowledge to make predictions • Scientists collect “facts” through observation and measurements

• Scientific Method: a systematic approach used in scientific study **Question or Problem • Observation: existing knowledge • Qualitative Data: information that describes color, odor, shape, and other physical characteristics • Quantitative Data: numerical information • Hypothesis: a tentative explanation for what has been observed, and that can be tested • Experiment: a set of controlled observation that test the hypothesis • Independent Variable: in an experiment, that variable the experimenter plans to change • Dependent Variable: in an experiment, the variable whose value depends on the independent variable • Control: in an experiment, the standard that is used for comparison • Conclusion: a judgement based on the information obtained

Scientific Theory vs. Law • Scientific Theory: explains a large number of facts and hypothesis • Has withstood much testing • Is synonymous to fact • Plate tectonics is a theory built of many hypotheses of plate motion • Scientific Law: describes a relationship in nature that is supported by many experiments • Law of Gravity • Newton’s Laws of Motion

A scientific inquiry • Step One: Collection or Observations - Dinosaurs extinct @ ~65 Ma - Many other organisms extinct @ ~65 Ma - Iridium (Ir) present at extinction - Iridium (a metal) is found in meteorites, comets, certain lavas, and cosmic dust. Not normally found in high concentration at Earth’s surface

A Scientific Inquiry • Step Two: Hypothesis development - Comet or asteroid impact created the iridium anomaly - Testable? - Side effects? - Dust cloud Fireball “Nuclear” winter Instant death

A Scientific Inquiry • Step Three: Observations and Experiments - Test for iridium world-wide - Test for abrupt end to dinosaurs and plankton - Crater?

A Scientific Inquiry • Steps Four & Five: Accept, modify, reject? - Iridium is world-wide - Almost abrupt end to dinosaurs and plankton - Later crater & soot found (Mexico's Yucatan Peninsula)

Forming the Universe

“…and it all started with the Big Bang” • Big Bang: a violent expansion of the universe • All matter and energy that now constitutes the universe was initially packed into an infinitesimally small point • The point expanded, according to current estimates, 13. 7 billion years ago • The universe was small, dense and hot. It only consisted of energy. • Within a few seconds, hydrogen began to form • By 3 minutes, the temperature fell to below 1 billion degrees, and the diameter grew to about 53 million km (35 million miles)

• Eventually (after several hundred thousand years) the Universe became cool enough for chemical bonds to bind atoms of certain elements together in molecules. • Stars first formed when gravity caused nebulae (cloud of gas and dust) of gases produced by the big bang to collapse inward, packing matter so tightly together that nuclear fusion reactions could begin • Nuclear fusion: process by which the nuclei of atoms fuse together, thereby creating new, larger atoms. • Stars and planets form when gravity pulls gas, dust, and ice together into a rotating disk. The center of the disk becomes a star. Rings around the star condense into solid planetesimals, which combine to form planets.

• Planetesimals grow by continuous collisions. Gradually, an irregular shaped Earth develops. The interior heats up and becomes soft. • Gravity reshapes Earth into a sphere. • Soon after Earth forms, a small planet collides with it, blasting debris into a ring around the earth • The moon forms from the ring of debris • Eventually, the atmosphere develops from volcanic gases. When the Earth becomes cool enough, moisture condenses and rains to create the oceans.

Misconceptions about the Big Bang • there was no explosion; there was (and continues to be) an expansion • Rather than imagining a balloon popping and releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe • we tend to image the singularity as a little fireball appearing somewhere in space • space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy - nothing.

Chapter 1 Forming the Earth

Origin of the Earth • The Earth is 4. 6 billion years old • It was formed by collisions of meteorites and other debris & particles • Earth started entirely molten and cooled into layers

Layered Earth • The Earth’s interior is layered • Each layer has a different chemical composition and physical property • We can classify the layers in 2 ways: • Compositional Layers: distinguished by different chemical composition • Mechanical Layers: differ in their strength or rigidity

Compositional Layers 1. Crust • The uppermost layer • Where we walk • It is like the skin of an apple. It is very thin compared to the other three layers • Oceanic Crust: heavy, dark colored rock containing magnesium and iron, thin(7 -10 km) • Continental Crust: lighter, light colored rock, containing silica, oxygen and aluminum, thick (20 -70 km)

Compositional Layers 2. Mantle • Middle Layer • Consists of oxygen, iron, magnesium, and silicon • Over 2900 km thick • The mantle = 68% of Earth’s mass and 83% of its volume!

Compositional Layers 3. Core • Inner most layer • Consists mostly of iron and nickel

Mechanical Layers 1. Lithosphere • Outer layer (100 -200 km thick) • Consists of the crust and upper mantle • Cool • Rigid (solid)

Mechanical Layers 2. Asthenosphere • Below the lithosphere • Middle mantle • Partially melted • “plastic” layer • 350 -650 km thick

Mechanical Layers 3. Mesosphere • Lower mantle • Hot as the asthenosphere but more rigid due to increased pressure , but still considered plastic

Mechanical Layers 4. Outer Core • Dense • Viscous liquid • Consists of iron and some nickel 5. Inner Core • Solid • Because there is so much pressure that it can only exist in the solid form • May reach 6600 C at its center • Consists of iron and some nickel