soil and weathering test Flashcards
Weathering
changes in rock material exposed at surface
mechanical weathering
physically changing rock into smaller pieces without changing its composition
Chemical weathering
breakdown of rock by changing its chemical composition
types of mechanical weathering
exfoliation, ice wedging, biological activity, abrasion
exfoliation
process where sheets of rock peel or flake away
ice wedging or Frost wedging
occurs when water seeps into rocks in freezes
biological activity
The activity of organisms that weather away rock
abrasion
collision of rock with one resulting in breaking and wearing away
types of chemical weathering
hydrolysis, carbonation, oxidation, acid precipitation, plant acids
hydrolysis
change in composition of minerals when they react with water
carbonation
when some minerals come in contact with carbonic acid they form a new product
oxidation
when metallic elements combine with oxygen – rust is one result of oxidation
acid precipitation
reacts with minerals
plant acids
plants secrete acids that you rode away the rock
rate of weathering depends on four things
Rock composition, and now of exposure, climate, topography
Rock composition
igneous and metamorphic rocks don’t weather easily sedimentary rocks do
amount of exposure
more exposure receives the faster it will weather
climate
slow and very hot/very cold climates but fairly rapid and warm, humid climates
topography
elevation or slope of surface where rock is located
regolith
A layer of weathered rock fragments that covers much of the earth surface
soil
part of the regolith that thatsupports plant growth – complex mixture of minerals, water, gases, and remains of plants and animals
essential to life on earth for growth
except for some steep mountain slopes and extremely cold regions, soil is found almost everywhere on earth surface
soil composition has four major components
mineral matter, organic matter/humanness, water, air
humus
dark organic material and remains of animals and plants
soil texture
Texter refers to the proportions of different particle sizes
particle sizes
Sand/large size – silt – Clay/small size – loan/a mixture of all three sizes and best suited for plant life
factors in soil formation
Parent material, time, climate, organisms, slope
Parent material
source of the mineral matter in soil
Time
The longer the soil has been forming the thicker if becomes
climate
greatest effect on soil formation and warmer temperatures equals faster soil formation but too hot can slow it down again
organisms
furnish organic matter to soil and plants are the main source
slope
steep slopes often have poorly developed soil’s
soil profile
A cross-section in which the layers of the soil in bed rock can be seen
each layer is called a horizon
in fully developed residue soil…
there are multiple horizons
soil that’s formed in place
horizons
o horizon/organic, thin, contains humus
A horizon/topsoil,mixture of decaying organic matter and small rock particles
B horizon/subsoil, contains minerals and Clay
C horizon/regolith, partially weathered bed rock
bed rock/parent material, solid, on whether to rock that lies beneath regolith
tropical( wet and warm ) climate
forms laterites ( thick and infertile soil )
dessert/dry climate
form saw whales from mechanical weathering – soil is thin and mostly regolith
temperate climates
temps range from cold to warm
two types of soil that are found depending on amount of rainfall
pedalfer and pedocal
pedalfer
soil form if an area receive 65 cm or more of rain per year
found in places east of the Mississippi
Pedocal
soil formed of rainfall is less than 65 cm a year
soil erosion
erosion is the process by which the products of weathering are transported
occurs worldwide
slow process
New soil forms about as fast as the existing soil erodes
agents of erosion
gravity, windy, glaciers, precipitation, ocean waves, currents, streams, groundwater
unwise use of the land leads to
climatic conditions upset natural balance
deposition
process by which sediment are dropped in a new location – occurs after erosion
mass movement
The downward movement of rock, regolith and soil due to gravity
mass movement is triggered by (as is all types of soil erosion)
saturated surfaces/excess water , steepness of the slopes, removal of vegetation, earthquake
rockfall
The fall of rock from a steep cliff – most rapid
landslide
sudden movement of masses of a loose rock and soil down the slope of the hill
slump
downhill movement of a large block of soil under the influence of gravity
mudflow
The rapid movement of a large mass of mud
creep
extremely slow downhill movement of unweathered rock material
weathering/erosion of mountains
weathering and erosion wear down rugged peaks to rounded peaks and gentle slopes
