EAOS 111 Earth Systems and Geologic Time

Energy

The Earth system is powered by one external source (the Sun) and two internal ones: radioactive decay, and gravitational energy (heat still being lost from planetary formation).

Scale

Processes in the Earth system act on length scales of microns to thousands of kilometers, and on time scales of milliseconds to millions of years.

Cycles

Constant movement of material and energy between reservoirs.

Hydrosphere

Oceans, lakes, rivers, and groundwater.

Atmosphere

Troposphere, stratosphere, and clouds. Holds gases, water vapor, and aerosols.

Geosphere

Continents, seafloor, sediments, lava, and soils.

Biosphere

Animals, plants, and bacteria, both terrestrial and marine.

Earth System Reservoirs

Components of the Earth system where matter and energy are stored, including the atmosphere, geosphere, hydrosphere, and biosphere.

Flux

The constant exchange of energy and matter between Earth’s reservoirs.

Sources

Reservoirs that donate energy or matter.

Sinks

Reservoirs that receive energy or matter.

Isolated System

Matter and energy are fixed and finite, an imaginary scenario but conceptually useful.

Closed System

Energy is freely exchanged and matter is fixed.

Open System

Free exchange of both energy and matter.

Short Timescales

Up to decades, studied using time series observations.

Long Timescales

Up to thousands of years, studied through written records and oral histories.

Deep Time

Billions of years, studied through the geologic record.

Dynamic Equillibrium

Natural cycles are not simple and remain in constant motion, seeking balance and stability.

Mineral

A naturally occurring, inorganic, crystalline solid, with a definable chemical composition.

Rock classification is distinguished by:

Process of formation and lithologic character.

Weathering

The process by which rocks are broken down into smaller particles through physical, chemical, or biological means.

Transportation

Movement of weathered sediments by air, water, or ice.

Deposition

Removal of sediment out of the material transporting it.

Settling

When detrital sediments fall out of their medium.

Chemical Precipitation

When chemical sediments come out of dissolved solution.

Lithification

The process through which sediments are transformed into solid rock through compaction, dewatering, and cementation.

Compaction

When sediments are squeezed under pressure to remove water and become solid rock.

Dewatering

Removal of water from sediments to create solid rock.

Cementation

When dissolved minerals precipitate from water to fill empty spaces in sediments and form solid rock.

Sedimentary Rocks

Rocks formed through the accumulation and lithification of sediment, can be identified by layering, granular texture, presence of fossils, or ripple marks.

Volcanic

Fast-cooling, fine-grained igneous rocks formed extrusively from lava.

Plutonic

Slow-cooling, coarse-grained igneous rocks formed intrusively from magma.

Pyroclastics

Volcanic materials such as ash, lava, and volcanic gases ejected rapidly from a volcano.

Plutons

Intrusions of plutonic igneous rocks cooled and solidified at depth.

Magma

Molten rock derived from melting within the crust or mantle.

Rock Deformation

Change in shape or volume or a rock from directed stresses (heat and pressure) to redistribute fluids and transform minerals.

Metamorphic Pressure

Caused by deep burial of a rock, about 260 atm per km of depth.

Metamorphic Heat

Plutons or geothermal gradient applying about 25 degrees celsius per km of depth.

Igneous Rocks

Rocks formed from the cooling of molten rock, can be identified by their texture or mineral composition.

Metamorphic Rocks

Rocks formed from the deformation of other rocks under heat and pressure, can be identified by their foliation, presence of shiny mica layers, or deformed structures.

Uniformitarianism

A geologic principle stating that the processes occurring today are the same that have been happening throughout deep time.

Geologic Record

Earth’s memory bank of processes, stored as rocks and fossils.

James Hutton

A Scottish geologist who observed that the Earth was shaped by continuous processes over long periods of time, laying the groundwork for modern geology.

Relative Age

Determining which rocks are older or younger based on the relationships between units.

Absolute Age

Determining the true age of a rock unit using geochronology.

Geologic Timescale

A timeline which provides a shorthand to communicate about deep time.

Geochronology

The science of determining the age of rocks, fossils, and sediments through various dating methods.

Superposition

A principle of geology stating that younger sediments are deposited on top of older sediments.

Original Horizontality

A principle of geology stating that sediments are first laid down flat, then deformed through uplift and erosion.

Inclusion

A principle of geology stating that magma intrusions are younger than their surrounding matrix.

Fault

The fracture and slide of a rock due to tectonic stress.

Unconformity

A point in the rock record where sediments were eroded or not deposited, representing a gap in the record.

Disconformity

An unconformity where sediment deposition stops and resume after a period of time, layers remain parallel.

Angular Unconformity

When new sediment is deposited on top of rocks which have been tilted by tectonic stress then eroded.

Non-Conformity

A type of unconformity where sedimentary rocks are deposited on top of igneous or metamorphic rocks.

Age of Earth

4.543 Ga (Giga-annum, billions of years)

Radioactive Decay

The loss of protons or neutrons in the nucleus of an atom resulting in transformation into a different isotope or element over time.

Faunal Succession

Fossils succeed each other vertically in a specific, reliable order that can be identified over very long distances.

Biostratigraphy

Microscopic phyto- and zooplankton evolve rapidly, so instances of evolution and extinction can be used as chronostratigraphic benchmarks.

Magnetostratigraphy

Magnetic minerals in oceanic crust and other rocks align with Earth’s magnetic polarity, which flips periodically.

Camels ordinarily sit down carefully, perhaps their joints creak

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous.

Principle of Radiometric Dating

The number of atoms of an unstable isotope decreases with time.

Radiometric Dating: N

The number of atoms of an unstable isotope.

Radiometric Dating: Lambda

Radioactive decay constant, the fraction of atoms that decay per unit time

Radiometric Dating: T_1/2

Half life, the amount of time it takes for half the original atoms to decay.

Radiogenic Isotope

The stable product of an element’s radioactive decay.

Parent Isotope

The unstable element which undergoes radioactive decay.