Test 2 Flashcards
Weathering
The physical breakdown and chemical alteration of rock at earths surface
Mass Wasting
The transfer of rock and soil down slope under the influence of gravity
Erosion
the physical removal of material by physical agents i.e. water, wind, ice
Mechanical weathering
Physical forces breaking down rocks
Frost Wedging
caused by the expansion of water when it freezes in between cracks, repeated freezing and thawing causes the expansion
Unloading (sheeting)
reduction in pressure from erosion allowing rocks to expand, causing outer layers of rocks to crack, this can create an exfoliation dome
Biological Activity
Plants wedging in between cracks and spreading them apart, plants can also create acids eroding the rocks
Chemical Weathering
Chemically transforming rock into one or more new compounds
Hydrolysis
Where hydrogen ions replace other cations in minerals, causing minerals to breakdown and change into other minerals, ex: feldspar to clay
Dissolution
where solids are completely dissolved into ions by acids
oxidation
reaction where the elements loses electrons, this can cause rust on iron materials
Soil contains
A combination of minerals, organic material, water, and air 50/50
Differential weathering
different minerals weather at different rates
Parent Material
Source of weather material that soils develop from residual soils, transported soils
Rates of weathering is controlled by?
Mineral Composition
Climate
Particle size
Residual Soils
Soil developed from bedrock
Transported soils
soils developed on unconsolidated sediments
Formation of Soils is the product of?
Parent Material
Time
Climate
Plants and animals
topography
Time
The amount of time that weathering processes have been operating
Climate
Most control on soil, temperature and wetness of soil
Plants and animals
Amount of organic activity effecting the soil
topography
soil develops poorly on slopes
Soil profiles
O Horizon
A Horizon
E Horizon
B Horizon
C Horizon
Bedrock
O Horizon
Mostly organic materials, upper horizon is plant litter lower is decayed organic material
A Horizon
Largely organic material, lots of biological activity
E Horizon
Mostly Minerals
Eluviation
Leaching
Eluviation
As water percolates through the solid
Leaching
Water dissolves soluble materials carrying it downward
B horizon
Subsoil, materials removed from the E horizon is deposited into the B horizon
C Horizon
Partially altered parent material considered regolith not counted as true soil
Bedrock
Unweathered Parent Material
Sedimentary Rock sources
Weathering
Transportation
Sedimentation(Diagenesis)
Deposition
Sediment
Material derived from the mechanical and chemical weathering of rocks which is deposited on the surface of the earth
Sedimentary Rocks
Rocks formed from the calcification of sediments. They are the end products of mechanical and chemical weathering processes
How does sedimentary rocks provide evidence to past events
Provide information about sediment transporting
Often contains fossils
How are sedimentary rocks economically important
They contain Coal, Petroleum and natural gas and are a source for Iron, Aluminium and Magnesium
Types of sediments
Detrital Sedimentary Rocks
Chemical Sedimentary Rocks
Detrital Sedimentary Rocks
Formed from sediment transported as solid particles
Chemical Sedimentary Rocks
Formed from sediment that was once in solution
How are detrital Rocks classified
by texture and composition
Conglomerate
Large rounded grains (clasts)
Breccia
Large angular grains in a fine grain matrix
Porosity
Percent of void space
Permeability
A measure of the ease by which fluid may flow through the rock
Lithification
The process of changing sediments into solid sedimentary rocks
Compaction
Weight of overlying sediment compacts sediments
Cementation
Precipitation of minerals amoung individual rocks binding together filling in cracks
Inorganic Processes
Evaporation and chemical activity
ex: limestones , cherts
Lithification of Sandstone
After deposition
Compaction
Cementation
Lithification of shale
-Wet Mud
-Weight of New Sediment
-Development if splitting surfaces
precipitation occurs in two ways
Organic
Inorganic
Inorganic Limestone
Crystalline limestone
Travertine
Organic Limestone
Coquina
Fossiliferous
Chalk
Crystalline Limestones
High concentration of calcium carbonate dissolved in water result in its precipitation - precipitated CaCO3 from water
Travertine
Fine grained calcum carbonate precipitated from ground water Ofter found in caves or hot springs, cave deposits, hot springs
Coquina
Loosely cemented shells and shell fragments
Fossiliferous limestones
Shell and other biogenic fragments glues cemented with calcite cement
Chalk
Microscopic shells and clay (shells from Foraminifera and coccoliths)
Dolostones
Made up of calcium magnesium carbonate mineral dolomite, similar to limestones but doesnt easily react to acids
Chert
Microcrystalline silica, most deposits are organic originating from micro organisms
Coal
Only rock made up of organic material rather than minerals, result from large amounts of plant material being buried for millions of years, develops in swamps
Evaporites
Evaporation of water containing dissolved elements trigger deposition/ precipitation of minerals, ex: halite and Gypsum
Sequence of precipitation from sea water
1.Calcite
2.Gypsum
3.Halite
4.Bitterns
5.Nitrates
Sedimentary structures
Features exhibited in sedimentary rocks that form during depositional processes
Beds(strata)
Layers of sediment that have accumulated in depositional environment
Bedding planes
Surface between layers
Graded Bedding
Particle size changes within a single sedimentary bed from coarse at the bottom to fine at the top
Cross bedding
Non horizontal layering within individual beds develop when there is unidirectional current during deposition
Ripple marks
Small waves of sand that develop on the surface of beds from moving water or air, current ripples steeper
MudCracks
form when wet mud dries out and shrinks
Fossils
As indicators of depositional environments can provide info on temp and local vegetation
Sedimentary Environments
A geographic setting where sediment accumulates
Depositional Environments
Places where sediments accumulate, different environments produce characteristic sedimentary rocks
Depositional Environment catagories
Continental
Marine
Continental
Dominated by stream erosion,
ex:river, alluvial fan lake, glacial, wind.
Marine
Shallow
Deep water
Shores
Considered transitional between continental and marine
Rivers
Detrital silts and sands, well sorted, rounded, crossbedding
Alluvial fan
Detrital streams going from high structures going down to a lower elevation depositing sediments quickly ( containing mostly gravel turning into a conglomerate)
Poorly sorted
Graded bedding
Lake
Detrital or chemical sediments
Fine grained size
well sorted
possible fossils
possible limestones
Delta
Fluvial and swamp environment river deposits inter bedded with coal
sedimentary Facies
A portion of a rock unit that has distinct set of characteristics that distinguishes it from other parts of the same unit
what can Sed Facies document
changes in sea level, environment etc.
Metamorphism
The solid state change in composition and / or texture of a rock due to high temps, pressures, or fluids in the earth
Agents of metamorphism
Heat
Stress
Fluids
