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Test 2

Terms in this set (49)

Metamorphic Rock
A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.

Low Grade: Very little change
Hight Grade: Massive amount of alteration
Changing of Rock Texture
Growth of mineral crystals -- grow by fusing together.
Alignment of Minerals --- 90 degree to pressure.
Formation of new minerals -- Change to temperature and pressure.
Type of Alteration
Heat Alteration --- Caused by proximity to magma.
Pressure Alteration -- Caused by deep burial or tectonic activity.
Chemical Alteration -- Often caused by reaction active fluids.
Type of Metamorphism
Contact Metamorphism ----nearby magma, Heat/chemical

Regional Metamorphism --nearby mountain, heat/ pressure/ chemical, show high grade.

Dynamic Metamorphism --show fault motion, Breccia and shattered.

Shock Metamorphism -- Alteration due to impacts. High-pressure rocks.
Foliated
Term used to describe metamorphic rocks whose grains are arranged in parallel layers or bands.

Rocks are slate,phyllite, schist,gneiss
Non-foliated
Term used to describe metamorphic rocks with grains that arranged randomly and do not split in layers.

React to Acid

Limestone or dolostone

Type of rock - Marble, quartet, hornfels
Weathering
A group of processes that cause rocks to disintegrate and decompose at the earth's surface.

(Not same as erosion)
There are two major types of weathering ?
Mechanical and Chemical
Mechanical Weathering
The disintegration of rocks and minerals into smaller pieces, without any substantial chemical change (granite becomes smaller pieces of granite.)

Frost Wedging
Growth of Mineral Crystals
Root Wedging
Thermal Expansion
Unloading
Frost Wedging:
Water in fractures expands as it freezes, causing rocks to break apart. This is a common process in mid-latitude climates.
Growth of Mineral Crystals
Similar to 1 but involving halite, gypsum,etc. This is common in drier climates.
Root wedging
The growth of plan life on most rocks will slowly widen pre-existing fractures, allowing water and roots to extend even deeper
Thermal Expansion
Rocks exposed to extreme daily temperature ranges may expand and contract enough to weaken their internal structures, similar to concrete and asphalt roads in summer.
Unloading
Release of confining pressure can cause intrusive igneous and metamorphic rocks to fracture and exfoliate. This is much more common in large masses of rock than smaller ones. Unloading often causes rocks to become more spherical in shape.
Chemical Weathering
The decomposition of rock by the alteration of its mineral components. Chemical weathering requires the presence of fluids, usually water. (Rock may be soil)
Solution
Oxidation
Hydrolysis
Solution
Some minerals dissolve when exposed to water. Naturally occurring water is usually slightly acidic due to dissolved carbon dioxide or other atmospheric Gases.
Oxidation
Many minerals that have a high iron content will oxidize, leading to the formation of hematite and/or goethite.
Hydrolysis
Some minerals will combine with water to form new minerals.
Example - Feldspar + Water = Clays
Factors Influencing Weathering Rates
A. Rock type - due to origin, texture and mineralogy.
1. Granite vs Gabbro in Ohio which one should survive more -----> Granite
2. Limestone vs Sandstone in ohio is sandstone is better.
3. Limestone vs Marble In ohio marble is better.
Sandstone vs conglomerate in ohio it hold better is Sandstone because conglomerate lose its stones.
Sandstones vs Shale -- in ohio sandstone hold better.
Sandstone vs quartzite -- in ohio quartzite hold better.
Climate
Warm humid climates have a much higher rate of chemical weathering than cold dry climates.
Topography
Rates are higher when more rock is exposed at the surface. Mountains have more rapid weathering than central Kansas.
Soil
Soil is created when weathered rock material is combined with organic matter, water and air.
Soil formation influenced by: Parent Material, Time, Climate, Slope
Parent Material
Residual Soil form slowly on bedrock.
Transported Soils from quickly on sediment.
Time
Parent material is less significant with time.
Climate
Influences depth and productivity of soils.
Slope
Influences formation rate and drainage.
O-Horizon:
Mostly organic matter, many not present in some
B - Horizon (subsoil)
The zone of accumulation.at teh c[horizon
Iron, clat, salst, etc from the E-horizon are deposited rate
C.Horizontal
Zone of soil formation mostly rock.region badrock and and.or bene
Relative Age
The sequence of past events in order from oldest to youngest. (Determined mainly by analyzing sedimentary rock layers and fossils. This can also work with extrusive igneous rocks, some intrusives and faults.)
Absolute Age
The age of events or objects, expressed as a number. (Usually determined using radiometric dating on igneous rocks. It can also be used on some sediment and soil, but it doesn't work well with some sedimentary or metamorphic rocks.)
Rock layers (beds)
Contacts - Surface separating rock layers.

Formation - Body of rock of considerable thickness with characteristics allowing it to be distinguished from adjacent rock layers.
Relative Age Principles
Original horizontality - Beds of sediment deposited in water form as horizontal layers are tilted, something caused that at a later time.
Superposition -
Within an undisturbed sequence of sedimentary or volcanic rocks, layers get younger from the bottom toward the top.
Cross-cutting relationships -
Igneous intrusions and faults are younger than the rocks they cut through.
Inclusions -
Fragments of other rocks included in a host rock are older than the host rock.
Uniconfromaties
Erosional surfaces that represent gaps in the geologic record.

The sequence of sedimentary rocks with complete record of the deposition

Sequence shows a break in the record as indicated by correlatable fossils
Disconformity
And unconformity that separates horizontal sedimentary rock layers from older horizontal sedimentary rock layers.
Angular unconformity
Separates overlying younger layers from tilted or folded layers that have been eroded.
Nonconformity -
and unconformity that separates igneous or metamorphic rocks that have been eroded and covered by younger sedimentary rocks.
Correlation
Determining the similarity of rock units within a region, continent or between continents.

Similarity of rock types - assumes similar sequences of rocks formed at the same time.

Correlation by Fossils -- Similar fossil assemblages can be used to back-up rock-based correlation.
Absolute Dating
Absolute Dating - puts numerical values (thousands or millions of years, etc.) on the age of rocks and geologic time periods.
Mass wasting
The down slope movement of material (rock, sediment, soul) due to gravity,
Influence by: Particle size and the degree of the slope
Type of mass wasting
Falls
Slides
Flows
Creep
Falls
The movements of individuals, detached pieces. Common along cliffs as rockfalls and debrisfalls.

Debris - Scree (talus)
Slides .
The movement of large amounts of material as unified and/or cohesive masses. They often occur due to pre-existing planes of weakness between rock layers, faults or fractures
Slump
movement of soil and sediment along a rotational surface, often breaking up near the base and transform into flows.
Rockslide
Often occur in areas of titled rock strata and regions of extensive faulting/fracturing.

They can move very rapidly and are often triggered by heavy rains and earthquakes.
Flows
Movement of sediment and soil as a fluid or chaotic mass. Flows are usually triggered by heavy rains or snowment.
Creep
The very slow (MM to C per year) movement of all surface material downslope due to wet/dry or freeze/thaw cycles in the uppermost soil or sediment layers.

Freeze/thaw cycles causes the land surface to alternately expand and contract. Gravity pulls the contracting surface downslope
Earthflows and mudflows
The more rapid movement of soil and loose sediment, often due to insufficient vegetation cover and heavy rains. Earthflows tend to involve long periods of sluggish movement, mudflows are often very rapid.
Debris flows
The very rapid movement of all surface debris, including large material such as bounders.

Derbies flows can occur anywhere there is a family steep slope, and can take place even in the presence of substantial amounts of vegetation.
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