Introduction to Earth Science Or, How The Earth Works

Branches of Earth Science Geology Solid Earth Much Larger than Other Parts Many More Kinds of Materials Preserves a History Meteorology – Climatology Oceanography Astronomy Planetary Geology

The Earth Systems External Effects (Astronomical) Atmospheric Circulation Oceanic Circulation Hydrologic Cycle Rock Cycle Plate Tectonics

The Solid Earth

Earth and the Universe (external effects) Earths’ Rotation (Day-Night) Lunar Effects (Tides) Annual Variation (Seasons) Precession and Orbit Variations (Ice Ages?) Galactic Rotation (250 m.y. period) Unpredictable Events Nearby Supernovae Meteor Impacts Long-Term Evolution of Sun

Atmospheric Circulation Unequal Solar Heating Equator to Pole Day - Night Different Surfaces Buoyancy Heating and Cooling Coriolis Effect High and Low Air Pressures Fronts and Air Masses

Oceanic Circulation Surface Currents - Driven by Winds Thermohaline - Deep Circulation Evaporation makes water more saline and denser Freezing makes water more saline and denser Cold water is denser than warm water

Surface Currents

Thermohaline Circulation

Hydrologic Cycle Evaporation from Oceans Precipitation on Land Infiltration into Ground (Ground Water) Runoff (Erosion)

Hydrologic Cycle

Water Principal Agent in Modifying Earth’s Surface Medium for Storing and Distributing Global Heat The Universal Solvent Essential for Life Destructive to Rocks Lowers Melting Point of Rocks Reduces Strength of Rocks Under Pressure

The Rock Cycle New Rocks Exposed by Erosion Rocks Broken Down Mechanically and Chemically (Weathering) Components Transported by Erosion Components Cemented into Sedimentary Rocks Burial and Heating creates Metamorphic Rocks Melting Creates Igneous Rocks

The Rock Cycle

Plate Tectonics Outer Crust of Earth Moves a Few cm/yr Driven by Convection in Earth’s Interior Accounts For: Earthquakes Volcanoes Mountain-Building (Orogeny) Configuration of Continents

Plate Tectonics

Plate Tectonics and Resources

Configuration of Continents Oceanic Circulation Weather and Climate Patterns Deserts Mountains and Rain Shadows Pathways for Migration Ecological Niches

Some Unique Aspects of Geology Importance of Relationships Sequential Spatial Importance of Time Distinctive Problems of Evidence Slow Rates Rare Events Destruction of Evidence Inaccessibility

Some Geologic Rates Cutting of Grand Canyon 2 km/3 m.y. = 1 cm/15 yr Uplift of Alps 5 km/10 m.y. = 1 cm/20 yr. Opening of Atlantic 5000 km/180 m.y. = 2.8 cm/yr. Uplift of White Mtns. (N.H.) Granites 8 km/150 m.y. = 1 cm/190 yr.

Some Geologic Rates Movement of San Andreas Fault 5 cm/yr = 7 m/140 yr. Growth of Mt. St. Helens 3 km/30,000 yr = 10 cm/yr. Deposition of Niagara Dolomite 100 m/ 1 m.y.? = 1 cm/100 yr.

1 Second = 1 Year 35 minutes to birth of Christ 1 hour+ to pyramids 3 hours to retreat of glaciers from Wisconsin 12 days = 1 million years 2 years to extinction of dinosaurs 14 years to age of Niagara Escarpment 31 years = 1 billion years

Some Unique Aspects of Geology (Continued) Reliance on Inference and Deduction Intrinsically "Unsolvable" Problems Ancient Landscapes Mass Extinctions Ancient Ocean Basins

Scientific Principles in Geology Parsimony (Keep It Simple) Superposition Uniformitarianism Using these, plus observation, we establish facts about Earth Processes

Parsimony The simplest explanation that fits all the data is preferred Doesn’t guarantee that things must be simple! Theories with lots of ad hoc or unsupported ideas are probably wrong.

Superposition: Road Cut, Superior, AZ

Geologic Map

Uniformitarianism Continuity of Cause and Effect Apply Cause and Effect to Future - Prediction Apply Cause and Effect to Present - Technology Apply Cause and Effect to Past - Uniformitarianism