From Brian Gilligan

Methods of Thermal Energy Transfer 3. RADIATION Heated objects radiate energy as well.

Methods of Thermal Energy Transfer Convection is the most important mechanism for geologic processes.

Rock Types and the Rock Cycle ROCK - a naturally occurring aggregate of minerals formed within the Earth. Delicate Arch, Arches Nat’l Park, UT Basaltic Dike Acadia Nat’l Park, Maine

A MINERAL is a naturally occurring, inorganic solid, consisting of either a single element or compound, with a definite chemical composition (or varies within fixed limits), and a systematic internal arrangement of atoms. Rock Types and the Rock Cycle

Diamond C Pyrite FeS 2 Beryl Be 3 Al 2 (Si 6 O 18 )

Three types of rocks. These are present in the crust and at the Earth’s surface. Each have fundamentally different origin. IGNEOUS SEDIMENTARY METAMORPHIC Rock Types and the Rock Cycle

Igneous Rocks - Cooled and solidified from MOLTEN material. - Formed either at or beneath the Earth’s surface. - MELTING of pre-existing rocks required. Granite Basaltic Lava

Sedimentary Rocks - Pre-existing rocks are weathered and broken down into fragments that accumulate and are then compacted or cemented together. - Also forms from chemical precipitates or organisms.

Metamorphic Rocks - Form when pre-existing Earth materials are subjected to heat, pressure and/or chemical reactions and change the mineralogy, chemical composition and/or structure of the material. Coal Gneiss Slate

Any rock type can become any other rock type given time and processes acting on them. These changes are reflected in the ROCK CYCLE.

Time and Geology For most geologic processes a great deal a time is needed. Earth is 4.6 billion years old. Time is available for these processes to operate very slowly. Geologists measure time in two ways: 1. RELATIVE AGE DATING 2. ABSOLUTE AGE DATING

Time and Geology Relative Age Dating: - Determined by spatial relationships between adjacent rock bodies and one another. - Provides relative age, no numbers involved. - Makes use of: Principle of Superposition Principle of Cross-Cutting Relationships Principle of Inclusions Principle of Original Horizontality

Relative Age Dating: Time and Geology

Absolute Age Dating: - Determine actual age of the rock or structure. - Provides absolute age, actual numbers of years are involved and applied. - Places rocks and events in Geologic Time Scale. - Makes use of: Radiometric techniques Tree-Ring Dating (Dendrochronology) Fission Track Dating Lichenometry

Time and Geology Absolute Age Dating: GEOLOGIC TIME SCALE - Subdivided into Era, Periods and Epochs - Based on fossil evidence, initially. - Actual years added using techniques mentioned earlier.

The Theory of Plate Tectonics Underlying unifying principle of geology. Evolved in the late 1960s, early 1970s. Realization that certain parts of the Earth were more affected by earthquakes and volcanoes. Also noted that large mountainous regions occur on margins of continents. Changes in sea level were related to these events. Was not a random occurrence.

Distribution of major volcanoes and earthquakes

The Theory of Plate Tectonics Many hypotheses presented to answer these questions. None answered all the questions at all localities. Led to hypothesis of PLATE TECTONICS. Became widely accepted in a few short decades.

The Theory of Plate Tectonics Steps in Development 1. Benjamin Franklin (late 1700s) Recognized that crust of Earth was a shell. Surface could be broken and parts moved about. 2. Alfred Wegener (1912) German meteorologist-geophysicist Proposed theory of Continental Drift. Proposed continents float on a denser underlying interior of the Earth. CONTINENTS periodically break up and DRIFT apart.

The Theory of Plate Tectonics Wegener believed all continents were joined together. Supercontinent of Pangaea existed about 200 myBP. Pangaea covered 40% of the Earth’s surface.