Earth Engineering - The Earth and Its Systems

Flashcards covering key vocabulary and concepts from the Earth Engineering lecture notes.

Earth's Systems

Civil, geological, and environmental engineers deal with all aspects of the earth's systems: 1. Lithosphere, 2. Hydrosphere, 3. Atmosphere, 4. Ecosphere, 5. Climate Change

Age of the Universe

Approximately 14 billion years old

Accretion of the Earth

Approximately 4.6 billion years ago

Oldest Rock Exposure on Earth

Approximately 3.5 - 4.0 billion years old

Chemically Differentiated Earth

Continents = granitic, Ocean crust = basalt, Mantle = iron-rich silicates, Core = iron and nickel

Convection

The dominant mechanism to redistribute thermal energy within the Earth.

Continental Rocks

Low density, older rocks (Na, K, and Ca silicates) concentrated by differentiation and recycling of lithosphere.

Ocean Basins

Denser, younger rocks (Fe and Mg silicates) formed by mantle plumes.

Isostasy

The state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates 'float' at an elevation which depends on their thickness and density.

Plate Tectonics

Lithosphere is broken into about 13 major plates that float on molten asthenosphere.

Divergent Plate Boundary

Move apart from one another

Transform Plate Boundary

Horizontal in opposite directions

Convergent Plate Boundary

Two plates come together

Mantle Drag

Convective currents possibly in the asthenosphere rise where heat production is greatest and sink where material is cooler

Ridge Push

Originating at divergent plates

Slab Pull

Relatively cool and dense oceanic crust sinks into the asthenosphere and 'pulls' the trailing lithosphere with it via gravity

Oceanic Divergent Plate Boundary

Constructive plate margin where seafloor is elevated to form oceanic ridges.

Continental Divergent Plate Boundary

Constructive plate margin forming a continental rift.

Convergent Plate Boundary

Destructive plate margin at subduction zone.

Transform Boundary

Lithospheric plates slide past each other along vertical fractures called transform faults.

Hydrologic Cycle

The continuous circulation of water between the oceans, atmosphere, and land.

Surface Runoff

Runoff that occurs when precipitation rates exceed infiltration rates.

Infiltration

The process by which water enters the subsurface soil and rock.

Evapotranspiration

The combined processes of evaporation and transpiration that deliver water to the atmosphere.

Urbanization

Urban development can severely affect the natural infiltration and runoff cycle

Atmospheric Circulation

The sun provides energy to the earth's surface via radiative transfer, leading to atmospheric circulation.

Hydrosphere and Oceanic Circulation

Climate is highly sensitive to ocean circulation and surface temperatures.

Oceanic Circulation

Warm, shallow currents driven by atmospheric circulation redistribute thermal energy.

Thermohaline Currents

Deep currents arising when water at arctic/antarctic freezes, becomes more saline, sinks, and completes circulation pattern.

Law of Superposition

In an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.

Principle of Original Horizontality

Layers of sediments are generally deposited in a horizontal position.

Relative Dating

Placing geological events into sequential order as determined from their position in the geologic record.

Absolute Dating

Results in specific dates for rock units or events expressed in terms of years before the present.

Principle of Cross-Cutting Relationships

Any geological feature that cuts across or penetrates a pre-existing second rock body is younger than the rock it penetrates.

Unconformity

A break or gap in the rock record caused by erosion and/or non-deposition of rock units.

Conformable Rock Record

A conformable rock record is continuous in age and has no breaks.

Angular Unconformity

Consists of tilted sedimentary rocks overlain by younger flat-lying sedimentary rocks.

Disconformity

Represents a time unconformity between parallel layers of sedimentary rocks.

Nonconformity

Exists between sedimentary rocks and metamorphic or igneous rocks.

Dating with Radioactivity

Dating is based on the decay rate of unstable (i.e., radioactive) isotopes.

Isotopes

Variable forms of an element, with different numbers of neutrons in their nuclei.

Radioactive Decay

The process by which an unstable atomic nucleus is spontaneously transformed into an atomic nucleus of a different element.

Half-life

The time it takes for one-half of the atoms of the original unstable parent element to decay to the atoms of a daughter element.

Global Climate Change

Describes trends and variations in Earth's climate, including temperature, precipitation, and storm frequency.

Global Warming

An increase in Earth's average temperature.

Greenhouse Gases

Atmospheric gases that absorb outgoing LW infrared radiation.

Milankovitch Cycles

Periodic changes in Earth's rotation and orbit around the Sun.