Chapter I: Earth As A System Flashcards
What is the fundamental principle guiding geologists in the reconstruction of Earth’s History?
Actualism
What are the 3 basic groups of Rock?
Igneous, Metamorphic, and Sedimentary
What is a Rock?
Interlocking, bonded grains; composed mainly of single elements and sometimes rock fragments.
What is a Mineral?
Inorganic elements or compounds characterized by internal structure and chemical composition.
How are Igneous rocks formed?
Extreme heat, molten magma that then cools to form rocks.
How are Metamorphic rocks formed?
Extreme heat and pressure causes metamorphosis of igneous or sedimentary rocks but does not cause melting.
How are Sedimentary rocks formed?
Weathering and erosion creates sediments which are then deposited and bonded together.
What 5 principles are used to determine the relative ages of rocks?
Steno’s 3 Principles; Superposition, Original Horizontality, and Original Lateral Continuity. And the Principles of Intrusive Relationships, and Inclusion.
How are changes in life recorded?
The fossil record, succession reveals relative age.
How are actual age’s of rocks estimated?
Radiometric dating through the use of radioactive decay.
How is the rock record divided?
Into discrete elements of time by the Geological time Scale.
What is an Unconformity?
A gap in the record of sedimentary (episodic) rock.
What are the three types of unconformities?
Angular; separates tilted beds below from flat beds above, indicates some sort of upheaval.
Disconformity; separation of two flat lying beds by an erosion surface. Usually indicates a change in environment (ocean floor to land for example).
Nonconformity; Separates flat lying bed from an eroded, crystaline rock below. Indicates a long period of erosion prior to deposition.
What is the Lithosphere?
The thin, rigid crust and upper mantle. Floats on the Asthenosphere.
What is the Asthenosphere?
About the upper 10% of the liquid mantle, partially liquefied.
What is the difference between Continental and Oceanic Crust?
Continental is much thicker and less dense than Oceanic Crust. Continental Crusts are formed primarily of Felsic rock (rich in feldspars, silicon and aluminum) while Oceanic Crusts are formed primarily by Mafic rock (rich in iron and other heavy metals).
Where does the heat inside earth originate?
Radioactive Decay
What drives plate movement of the lithosphere.
Intense heat and convection within the Asthenosphere.
Actualism
Chemical and physical principles we see today do not vary over time. Key to studying earth’s history.
Catastrophism
Championed by Werner, most visible rocks at earths surface were formed by global floods and supernatural powers.
Uniformitarianism
Early form of actualism championed by Lyell. Problematic in the fact that it does not allow for catastrophic change or variable rates of change over time.
Bedrock
interconnected set of rocks below loose sediment and soil, exposed in outcroppings and exposures
Extrusive vs Intrusive Igneous Rock.
Extrusive rock forms after reaching earth’s surface, faster cooling leads to smaller crystalline structures. Intrusive rock forms beneath the earths surface, cooling is generally slower and structure is larger.
Weathering vs Erosion
Weathering is the chemical of physical breakdown of rocks while erosion loosens fragments of rocks and then moves them down hill.
Rock Cycle
Links all types of rocks to each other
Sediment transports
Crystalline Rocks
Grouping of Igneous and Metamorphic Rocks
Discrete episodes of sediment
Strata (Stratum pl), or beds
Rock Formations
Discrete bodies of rocks.
Super Groups>Groups>Formation>Members
All Discrete
Stratification
Arrangement of sedimentary rocks within discrete layers
What are the 3 types of Sediment
Detrital; most common formed through weathering
Biogenic; formed by skeletons of dead organisms
Chemical; (inorganic); precipitated chemically from water
What is an example of a chemical sediment?
Salt Flats
What is an example of a biogenic sediment?
Limestone
What is an example of a detrital sediment? (chemical origin and physical orgin)
Chemical: Shale formed by Clay
Physical: Sandstone formed by Sand
Two most common due to large amounts of Quartz (sand) and Feldspars (Clay) in granite.
Steno’s 3 Principles
Basis of Stratigraphy
Superposition; strata age increases with depth
Original Horizontality; strata originally more horizontal than vertical
Original Lateral Continuity; strata originally taper to 0 or abut a natural basin
Principle of Intrusive Relationships
invasive rock is always younger than country rock
Principle of Inclusion
Fragments of rock found within another rock are always older than the rock they are enveloped by
Principle of Cross-Cutting Relationships
A structure which cuts through an existing sequence of rocks is always younger than the rocks it cuts through
Xenolith
inclusions of country rock by igneous rock
Units of Geological Time
Eon>Era>Period>Epoch
Geological System
Body of rock designated to a certain geological time
Moho Discontinuity
the increase of a seismic wave’s velocity as it passes from the crust to the denser mantle. (slows again as it hits the Asthenosphere)
Isostacy
Balance of the lithosphere on top of the asthenosphere, maintained by extensions into the asthenosphere beneath thicker sections of crust. (Roots beneath Mountains)
Spreading Zones
areas where plates move apart, generally creates volcanoes and thicker sections of lithosphere at mid-ocean ridges
Subduction Zones
areas where one plate slides underneath another into the asthenosphere, generally form mountains and volcaonoes
Slabs
portions of plate which have extended into the asthenosphere
Plumes
formed by a slab breaking off and sinking into the asthenosphere then melting. The less dense molten material of the slap rises to the top of the asthenosphere quickly creating a hot spot.
Transpiration
Release of water vapor from plants that was taken from ground water
Evaporites
Salts that constitute sedimentary deposits by accumulating into layers
Fresh Water
water containing less than .05% salt by weight
What type of rock are most fossils found in?
Sedimentary rock, most fossils cannot survive the high heat/pressure required to form crystalline rocks.
What features distinguish one geologic system from another?
Unique groups of fossils and the nature of the rocks themselves.
What drives the water cycle and how does it relate to geologic and biological processes?
Evaporation, Transpiration, and Precipitation. It causes weathering/erosion and greatly affects the climate and weather patterns of Earth.
