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135 Cards in this Set
- Front
- Back
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Geology is..
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-The study of the earth
-observational and integrated science -earth is a product of 4.56 billion years of geothermal evolution |
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Hydrologic cycle
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-movement of the earth's water and gas layer
-powered by solar radiation with minor geothermal energy -sculpts continental land surface |
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Differentiated Planet - Layers
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Top to Bottom -
Continental Crust - Oceanic Crust Rigid Upper Mantle Asthenosphere Transitional Mantle Lower Mantle Outer Core Inner Core |
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Interactive Spheres of the Earth
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Lithosphere
Asthenosphere Hydrosphere Cryosphere Atmosphere Biosphere |
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Lithosphere
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Crust - oceanic and continental
Rigid Upper Mantle |
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Asthenosphere
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Hot plastic layer of upper mantle
Capable of slow flow/convection |
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Cycles or Systems of the Earth
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Tectonic Cycle
Hot Spot Cycle Hydrologic Cycle |
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Tectonic Cycle
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-Motion of earth's fragmented
-Lithosphere over asthenosphere -Divergent and Convergent Plate Boundaries |
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Divergent Plate Boundary
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Spreading!
New crust created where two plates pull apart from each other -creates ridges and rifts/rift valleys |
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Convergent Plate Boundary
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Plates diving under each other
causes subduction zones. mountains and volcanoes often form |
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Oceanic-Continental Convergence
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Continental Margin Subduction
Makes oceanic trench and continental volcanic arc |
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Oceanic-Oceanic Convergence
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Oceanic Subduction
one plate subducted under another to form deep oceanic trench also cause undersea volcanoes, volcanic island arc |
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Continental-Continental Convergence
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Continental collision
create mountain ranges |
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Active Continental Margin
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leading edge, where crashing into oceanic plate
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Passive Continental Margin
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remaining coastline, no collision or subduction
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Hot Spot Cycle
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stationary convecting mantle plumes that rise from deeper than the asthenosphere
create landforms known as linear volcanic chains or hot spot tracks |
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Hydrologic Cycle
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Evaporation, Transpiration, Precipitation
water storage in atmosphere/snow/ice, run off groundwater POWERED BY SUN |
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Water Reservoirs
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Oceans (95% of free water)
Glaciers Groundwater Lakes/Rivers Atmosphere Biosphere |
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Hydrologic Cycle Sub-Systems
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Weathering
Mass Wasting River Systems Glacial Systems Groundwater Systems Ocean System Wind System |
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Parts of Continental Crust
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Continental Basement
Stable Platform |
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Continental Basement
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ancient eroded roots of mountain ranges
mainly igneous intrusions and metamorphic rocks, the exposed continental basement is known as the shield |
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Stable Platform
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thin veneer of young, undeformed, flat-lying sedimentary rocks within the continental interior
makes up the Great Plains of North America |
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Deformation
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Rocks bending and breaking in response to compression, tension or shearing.
produces joints, faults, folds and foliation |
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Earth Minerals
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important to landscape development because
--material being sculpted. has varying strengths/weakness --composition, texture, structure control weathering and erosion rate |
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Minerals
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basic building blocks of rocks
solids with elements arranged in varying ways (crystalline clastic etc) |
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Ionic Bonds
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Positive and negative charge
Weak bond, less resistant to weathering Often expressed in minerals as cleavage |
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Covalent Bonds
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Shared electron
Strong bond, more resistant to weathering The harder the mineral - the more like to possess covalent bonds |
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Cleavage
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Reptitious breaks along weak bonds
weathering hits there first |
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Silicate Minerals
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Quartz
Feldspar Olivine Mica Wide variety but many strongly covalently bonded --> resistant to weathering |
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Silicate Minerals vs. Other Minerals
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Silicates more resistant, have more covalent bonds
Others less resistant, have more ionic bonds |
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Carbonate Minerals
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Calcite,
ex : mineral calcite of limestone, evaporite minerals or shells weak mineral, lots of ionic bonds. |
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Sulfate Minerals
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Mineral gypsum of gypsum rock
precipitate from evaporating saline solutions |
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Halite Minerals
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Mineral halite of rock salt
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Most Resistant Silicate Minerals?
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Quartz is most resistant, many covalent bonds.
Feldspar also quite resistant, less so because of cleavage (evidence of ionic bonds) More resistant = harder, no cleavage |
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Igneous Rocks
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formed by cooling of silicate melt (magma/lava)
composed of silicate minerals product of plate tectonics/hotspots |
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Rocks have 3 Features:
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Texture
Structure Composition |
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Rock Texture
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grain to grain relationship
i.e. crystalline, clastic, foliated, etc. |
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Rock Structure
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overall fabric of rock, larger feature than texture
ex. layers in rocks |
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Rock Composition
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What minerals is it made of?
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Igenous Crystalline Texture
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texture with random interlocking minerals.
very little space between minerals low porosity/permeability |
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Magmatic Differentiation
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process by which different types of igneous rock are derived from one parent magma
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Plutonic vs. Volcanic
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Plutonic (Intrusive) - silicate melt (magma) cools slowly underground
Volcanic (Extrusive) - silicate melt (lava) cools rapidly at earth's surface |
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Plutonic Textures
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Igneous Crystalline Phaneritic Texture (coarse grained)
is very resistant to weathering |
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Plutonic Structure
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Instrusive Contact
composition variation, normally a weakness in rocks |
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Plutonic Landforms
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Dikes, domes, batholiths,
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Igneous Crystalline Phaneritic Texture
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coarse grained
5mm very resistant to weathering due to interlocking nature, silicate composition |
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Basaltic Volcanism
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lava more fluid and capable of flowing long distances
low gas content makes eruptions not very explosive dominated by quiet lava flows |
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Common Mafic/Basaltic Volcanism Landforms
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Shield volcano
plateau lava field - thick piles of flat lying lava |
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Common Mafic/Basaltic Textures
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Igneous Crystalline Aphanitic Texture
resistant to weathering |
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Igneous Crystalline Aphantic Texture
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fine grained
2mm resistant to weathering because of composition and interlocking, less than phaneritic bcause fine grained |
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Common Mafic/Basaltic Volcanic Structures
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flow breccia - fragmented top and bottom of many lava flows
cooling joints (columns) - cooling fractures create porosity |
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Intermediate to Silicic Volcanism
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Eruptive lava flows are thicker, pastier lavas and do not flow far
Eruptions can also be very explosive (pyroclastic) |
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Common Intermediate/Silicic Volcanic Landforms
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Stratovolcano
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Igneous - Unwelded Pyroclastic Texture
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lots of open space allows for rapid weathering
contains fragments of glass |
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Igneous Welded Pyroclastic Texture
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pumice and ash shards compressed
reduces porosity and weathering |
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Igneous Structures
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often provide weakness allowing water to infiltrate and increase weathering, mass wasting
-igneous contacts -flow breccia -cooling joints (fractures) -gas bubbles (vesicles) |
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Sedimentary Rocks
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Formed by the compaction and/or cementation of sediment
Weakest of 3 rocks because 1) commonly composed of fragmented peices creating porosity 2) stratification |
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Sources of Sediment
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mechanical and chemical weathering
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Types of Sedimentary Rocks & Textures
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Clastic Sedimentary - Clastic Texture
Chemical Precipitates - Sedimentary Crystalline Texture Organic Precipitates - BIoclastic & Crystalline Textures |
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Clastic Sedimentary - Clastic Texture
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resistance to weathering depends upon the amount and type of cement
generally porous and permeable shale and siltstone are easier to erode than sandstone |
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Chemical Precipitates - Sedimentary Crystalline Texture
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Interlocking, random oriented carbonate, sulfate, or halide minerals.
May be resistant, especially in areas of low rainfall. Originally have low porosity, but subject to dissolution because of weak bonds |
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Organic Precipitates - Bioclastic Texture
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Fossil fragments in a matrix of crystalline calcite mud.
Bioclastic often resistant cliff formers, especially in areas of low rainfall. originally may have limited porosity, but composed of calcite so dissolution can occur |
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Structures of Sedimentary Rocks
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Depositional Layering or Stratification -
The layering allows water to penetrate the rock & weaken it. the more stratification and the thinner the stratification....the weaker and less resistant is the rock to weathering and erosion. |
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Depositional Environments
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a portion of the earth's surface characterized by a unique combination of physical, chemical, and biological processes.
control how sediment is transported and deposited, chemical modifications, and organisms in sediment |
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Metamorphic Rocks
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Formed by the recrystallization of pre-existing rocks in the solid state;
generally formed in the roots of mountain ranges at convergent plate boundaries crystalline, mostly silicate -- can be strong, depends on structure/texture |
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Factors Influencing Metamorphism
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Increasing Temperature
Increasing Pressure Chemically Active Fluids |
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Adjustments to the Prolith (original rock) during metamorphism
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Recrystallization and formation of:
New minerals New Textures New Structures |
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Regional Dynamothermal Metamorphism
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Most common form of metamorphism of rocks in the roots of mountain ranges
Recrystallization due to increases in pressure, temperature, and/or chemically active fluids produces crystalline textured rocks |
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Dynothermal Metamorphism ---Metamorphic Foliated Texture
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interlocking minerals that are aligned in planes
dominated by platy or elongate minerals planar feature exploited by water, less resistant to weathering |
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Dynothermal Metamorphism -- Metamorphic Nonfoliated Texture
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crystalline interlocking minerals (aligned)
dominated by equant-shaped minerals more resistant to weathering -- non planar and one mineral, usually |
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Metamorphic Structure
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Axial Planar rock cleavage/foliation
The metamorphic alignment of minerals along the axis of tight folds major weakness in metamorphic rocks |
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Dynamic Metamorphism
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Change in the rock due to shearing in fault zones
In the upper crust, where temperature and pressure are low, it results in crushing and fragmentation of the rock Weakens the rock and allows for greater weathering. Flaser structure : elongation of minerals like net. weakens rock |
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Mechanical Weathering vs. Chemical Weathering
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Chemical - chemical alteration of rock and or sediment
Mechanical - physical breakdown |
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Ice Wedging
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expanding ice propagates existing fractures
Common in climates and elevations that undergo numerous freeze and thaw cycles |
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Tectonic Joint Development
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rocks subjected to tectonic stresses and are deformed to produce fractures without displacement
square shape |
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Cooling Joint Development
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cooling of hot rock masses. only in igneous rocks
commonly expressed as vertical columnar joints |
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Sheeting (unloading) Joint Development
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overburden pressure is removed rapidly by uplift and erosion allowing the rock to expand outward
Best displayed in large igneous intrusive rocks with phaneritic texture and limited structures rock pushes through ground, causing sheet joints/exfoliates. parallel to ground |
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Biologic Activity
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growth of tree/plant roots; burrowing of animals, human activity
also lichen (decay, producing organic acids which help in weathering) |
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Thermal Expansion and Contraction
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the expansion of rock upon heating followed by the contraction of the rock upon cooling.
Known to occur during large firestorms Questionably occurs in arid regions with large differences in daytime/nighttime temperatures. |
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Salt Crystallization
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Growth of minerals (“salts”) in the pore space of rocks forcing apart grains
Common in splash zones of shoreline systems and near springs in arid regions |
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Chemical weathering
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Chemical decomposition of unstable minerals at the Earth’s surface to become stable minerals
hydrolysis oxidation dissolution |
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Hydrolysis Weathering Reaction
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example: feldspar to clay
take unstable minerals and change to stable minerals and dissolved ions in water |
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Oxidation Weathering Reaction
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example: iron to rust
take unstable minerals, changes to stable minerals and dissolved ions in water |
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Dissolution Weathering Reaction
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example: calcite.
dissolve the mineral. salt into water leaves behind a pitted surface |
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Effect of Climate on Weathering
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-most important factor
-controls rainfall and temperature -water and temperature is key factor in weathering |
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Effect of Composition on Weathering
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Different minerals have different stabilities at Earth's surface
different minerals weather differently and have different properties |
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Effect of Texture on Weathering
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manner in which minerals are touching one another
different arrangements allows for different porosities and permeabilities differing amounts of water --> different weathering |
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Effects of Structure on Weathering
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Structural weaknesses allow for more water to come in
can break apart rocks, creating more surface area and finer pieces to make weathering more possible |
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Effects of Topography on Weathering
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topography is slope of the land surface
influences how long the weathered material stays in place and can continue to weather also, rate at which things will go down hill. steeper --> faster weathering |
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Effects of Time on Weathering
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in general, the longer the time materials are exposed, the greater the degree of weathering and the development of soil formation
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Product of Weathering : Regolith
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any loose unconsolidated sediment
formed by break down of rocks |
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Product of Weathering: Soil
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regolith mixed with clay and organic matter
variety of soil is dependent upon climate, rock type that is weathering |
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Soil Horizons
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o, a, e, b, c
mature soil profiles have soil horizon also, better on gentle to flat slope |
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Spheroidal Weathering
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-onion skin or exfoliation surface
Common in rocks with feldspar... Hydrolysis of feldspar produces clay and a volume increase, joints erode first. water penetrates the rock from all angles. opens creating “onion skin” or exfoliation surfaces. |
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Sheeting "Exfoliation" Domes
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half dome - large bare rock circles
produced by unloading joint formation with aid from the freeze and thaw cycle |
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Weathering Rinds
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outer surface of rocks that have undergone chemical weathering while the interior is less altered (part that is exposed)
result of oxidation reaction |
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Differential Weathering
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rocks weathering at different rates due to differences in composition, texture, and/or structure
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Texture Effect on Differential Weathering
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different porosity/permeability effects weathering rate
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Composition Effect on Differential Weathering
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Different minerals have different % ionic and covalent bonds
therefore, will weather at different rates |
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Grain Size Effect on Differential Weathering
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fine grained particles weather quicker than coarse grained
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Contour Lines
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Line of equal elevation of topography
Every fifth line is bolder and usually labeled - index contour |
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Contour Interval
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Vertical elevation difference between contour lines
Index contour – every 5th contour is darker/labeled |
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Gentle vs. Steep Slopes
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Steep slopes – closely spaced contour lines
Gentle slopes – wide spread contour lines |
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Recognition of Hilltops on topo map
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closed contour lines indicate hilltop
make circles, ellipses, etc. |
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Recognition of Depressions
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closed contour lines where contour lines have “hachure marks”
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Recognition of Valleys and Ridges
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Look @ Elevation
ridges – V’s of contour lines point downhill valleys – v’s of contour lines point uphill |
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Fractional/Ratio Scale
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1: 24,000
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Graphic Scale
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scale at bottom of map.
use ruler |
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Size of Maps
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Uses minutes
1o (Degree) = 60’ (Minutes) 1’ (Minute) = 60’’ (Seconds) |
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Universal Transverse Mercater System
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x-y grid system established in meters
origin of the grid is located in the equatorial Pacific Ocean (all the numbers measured in meters from origin are therefore positive integers) World is sub-divided into 60 UTM zones, each of which is 6o of latitude wide. |
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Public Land Survey System (Township and Range)
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• x is located at : SW ¼, SE ¼, sec 11, T1S, R2W
• smallest to largest when figuring out where x is |
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Geographic North and Magnetic North
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This angle (and the date it was calculated) can be located at the bottom of the topographic map.
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Erosion
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The removal of regolith by some activity of the surface processes such as gravity (mass wasting), running water, ice or wind.
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Mass Wasting
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Downslope movement of material under the influence of gravity.
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Gravity and Mass Wasting
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Shear Stress - force acting to cause the movement parallel or down the slope
As the slope angle increases, the shear stress component increases and movement is more likely. Shear strength is prevention motion; internal resistance to movement THINGS WANT TO GET DOWNHILL. force of gravity pulls down --> mass wasting |
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Water and Mass Wasting
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too much water causes landslides, no friction, nothing to grab
mushy mess will fall down and increase mass wasting |
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Types of Mass Wasting
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Slope failure
Sediment flow |
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Slope Failure
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The sudden failure of a slope
results in the downslope transfer of relatively coherent masses of rock and/or rock debris Falls, Slides, Slumps |
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Slope Failure --> Rock Falls
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Rocks loosened by weathering processes (i.e. tectonic joints?) fall to the base of a resistant cliff face
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Slope Failure --> Slides
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Movement of coherent material along a generally flat planar slip face
(often stratification, sheeting joints, tectonic joints, foliation, etc.) Rock and Debris Slides |
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Slope Failure --> Slumps
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Coherent block that moves and rotates along a curved failure plane
The upper surface of each slump block remains relatively undisturbed, as do the individual blocks. Heavy rains or earthquakes usually trigger slumps. |
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Sediment Flows
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The downslope mixture of sediment, water, and air; no internal consistency to the material;
Granular Flows Slurry FLows |
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Sediment Flows --> Granular Flows
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water-understatured sediment flows
Debris Avalanche Earth Flow Creep |
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Sediment FLows --> Granular Flows --> Debris Avalanche
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Very large, rapidly moving mixtures of rock, regolith, and other debris
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Sediment FLows --> Granular Flows --> Earth Flow
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Slow (1m/hr to 1m/yr) mixing of regolith or debris downslope that usually produces a lobe at the base of the slope.
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Sediment FLows --> Granular Flows --> Creep
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Very slow (< 1cm/yr) movement of weathered soil or regolith downslope due to expansion and contraction of the material
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Sediment Flows --> Slurry Flows
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water saturated sediment flows
Debris Flows Lateral Spreads Submarine Mass Wasting |
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Sediment Flows --> Slurry Flows --> Debris Flows
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mudflows or lahars
fast moving slurry flows |
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Sediment Flows --> Slurry Flows --> Lateral Spreads
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Special variety of mass wasting event associated with the shaking and liquefaction of quick clays during an earthquake
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Sediment Flows --> Slurry Flows --> Submarine Mass Wasting
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Mass wasting events that occur on slopes beneath the water
material may start out above water and move into the water, or it may take place entirely underwater. |
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Influence on Mass Wasting:
Lithology (composition and texture) |
1. determines the products of weathering (regolith) that will be moving down slope
2. if the slope is solid bedrock, lithology helps determine the strength and resistance to movement 3. in part controls the porosity and permeability of the rock or regolith units |
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Influence on Mass Wasting:
Structural Weaknesses |
Planes of weakness that can be used to aid in mass wasting events
especially dangerous when layering is oriented in the same direction as slope of land |
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Influence on Mass Wasting:
Climate and Water |
climate influences weathering
controlling the amount and type of vegetation, and the amount of water (and rate it is supplied) in a region water Water: 1) lubricates surfaces and decreases frictional resistance 2) produces swelling of expandable clays 3) dissolves cement that binds clastic rock fragments 4) increases pore pressures in rock and regolith 5) add mass to a slope 6) controls the location of the water table, location of springs, etc. |
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Influence on Mass Wasting:
Over steepening of Slope |
Slope is in dynamic equilibrium trying to maintain a stable angle of repose.
Slope angles are changed over time by both natural and man-made events |
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Influence on Mass Wasting:
Triggering Mechanisms |
Earthquake
Volcano Excessive Rainfall |
