Introduction Introduction To Physical GeologyTo Physical Geology

Starring Professor Sean TveliaStarring Professor Sean Tvelia

The ScienceThe Science

►Geology is typically broken up into Geology is typically broken up into two fields of studytwo fields of study Physical GeologyPhysical Geology Historical GeologyHistorical Geology

Physical GeologyPhysical Geology

► Examines the materials Examines the materials composing Earth and seeks to composing Earth and seeks to understand the processes that understand the processes that operate beneath the surfaceoperate beneath the surface

It is the how and why of GeologyIt is the how and why of Geology

Historical GeologyHistorical Geology

► Seeks an understanding of the Seeks an understanding of the origin of Earth and its origin of Earth and its development through time.development through time.

It is the who, what, where, and whenIt is the who, what, where, and when

Why bother at all?Why bother at all?

►Many of the problems and issues Many of the problems and issues addressed by geology involve addressed by geology involve natural hazards, resources, world natural hazards, resources, world population and environmental population and environmental issues.issues.

The Scientific MethodThe Scientific Method

QuestionsQuestions Collection of DataCollection of Data Development of HypothesisDevelopment of Hypothesis Testing of HypothesisTesting of Hypothesis

► Science assumes the natural world is Science assumes the natural world is consistent and predictableconsistent and predictable

► Therefore our goal is to discover Therefore our goal is to discover ‘patterns’ that we can then use to ‘patterns’ that we can then use to make predictionsmake predictions

Geology Through TimeGeology Through Time

Two major schools of thoughtTwo major schools of thought► CatastrophismCatastrophism► UniformitarianismUniformitarianism

James HuttonJames Hutton► Dynamic/Cyclic Concept of Earth HistoryDynamic/Cyclic Concept of Earth History► Used principle of actualism (uniformitarianism)Used principle of actualism (uniformitarianism)

Earth as a SystemEarth as a System

Earth’s Four SpheresEarth’s Four Spheres► AtmosphereAtmosphere

The air we breatheThe air we breathe

► HydrosphereHydrosphere The water we drinkThe water we drink

► BiosphereBiosphere lifelife

► Solid EarthSolid Earth Where we liveWhere we live

All of these spheres interact with each other. A minor adjusting In the properties of one could lead to drastic changes in the Properties of the other three

PowerPower

External processes powered by the External processes powered by the SunSun

AtmosphereAtmosphere HydrosphereHydrosphere BiosphereBiosphere

The Earth system is also powered by The Earth system is also powered by Earth’s interiorEarth’s interior

Heat remaining from the formation of the Heat remaining from the formation of the planet and heat that is continually generated planet and heat that is continually generated by radioactive decay powers:by radioactive decay powers:► VolcanoesVolcanoes► EarthquakesEarthquakes► Mountain buildingMountain building

How did it all startHow did it all start

►Current belief is that the Earth and Current belief is that the Earth and the entire solar system were born the entire solar system were born at relatively the same time.at relatively the same time. All objects within our solar system All objects within our solar system

were formed from an enormous cloud were formed from an enormous cloud of gas and dust called a Nebula.of gas and dust called a Nebula.►Hence the name Hence the name Nebula HypothesisNebula Hypothesis

Once upon a timeOnce upon a time…5 billion years ago…5 billion years ago

►This enormous cloud began to This enormous cloud began to contract and spincontract and spin This contraction caused the nebula to This contraction caused the nebula to

spin faster (kind of like an ice skater spin faster (kind of like an ice skater spinning)spinning)

Eventually the inward contraction was Eventually the inward contraction was balanced by the outward force of the spinbalanced by the outward force of the spin►This forced the nebula to take on a disc This forced the nebula to take on a disc

shaped appearance shaped appearance

Lets go to the video tapeLets go to the video tape

Formation of Earth’s LayersFormation of Earth’s Layers

►As material accumulated to form the As material accumulated to form the Earth, the high velocity impacts and Earth, the high velocity impacts and decay of radio active elements decay of radio active elements caused the Earth’s temperature to caused the Earth’s temperature to steadily increase.steadily increase.

This heating caused the melting of many This heating caused the melting of many of the heavier elements: Iron, Nickelof the heavier elements: Iron, Nickel►Heavier elements sank, lighter elements and Heavier elements sank, lighter elements and

compounds remained at the surfacecompounds remained at the surface

Three principal Three principal compositional layers:compositional layers:

► CrustCrust – the comparatively thin outer skin that – the comparatively thin outer skin that ranges from 3 kilometers (2 miles) at the oceanic ranges from 3 kilometers (2 miles) at the oceanic ridges to 70 kilometers (40 miles in some mountain ridges to 70 kilometers (40 miles in some mountain belts) belts)

► MantleMantle – a solid rocky (silica-rich) shell that extends – a solid rocky (silica-rich) shell that extends to a depth of about 2900 kilometers (1800 miles) to a depth of about 2900 kilometers (1800 miles)

► CoreCore – an iron-rich sphere having a radius of 3486 – an iron-rich sphere having a radius of 3486 kilometers (2161 miles)kilometers (2161 miles) Average density is nearly 11 g/cm3 and at Earth’s center Average density is nearly 11 g/cm3 and at Earth’s center

approaches 14 times the average density of waterapproaches 14 times the average density of water Mostly iron, with 5 to 10 percent nickel and lesser amounts Mostly iron, with 5 to 10 percent nickel and lesser amounts

of lighter elementsof lighter elements

The surface of the EarthThe surface of the Earth

► Earth surface has two obvious divisionsEarth surface has two obvious divisions ContinentsContinents

► Most prominent features are linear Most prominent features are linear mountain belts and shieldsmountain belts and shields

Ocean BasinsOcean Basins► Ocean ridge system- the most prominent Ocean ridge system- the most prominent

topographic feature on Earthtopographic feature on Earth► Deep-ocean trenchesDeep-ocean trenches

► Significant difference between the Significant difference between the continents and oceans continents and oceans One is Wet : )One is Wet : ) their relative levels (how high is the ocean)their relative levels (how high is the ocean)