Chapter 6 test 2 Flashcards
(32 cards)
weathering
external process
physical breakdown and chemical alteration of rock at or near the earths surface.
mechanical and chemical
mass wasting
external process
transfer of rock and soil downslope under the influence of gravity(landslides)
Erosion
external process
the physical removal of material by mobile agents such as water, wind, ice or gravity
mechanical weathering
breaking of rocks into smaller pieces
frost wedging, sheeting, salt crystal growth, biological activity
frost wedging
alternate freezing and thawing of water in fractures and cracks promotes the disintegration of rocks.
sheeting
exfoliation of igneous and metamorphic rocks at the earths surface due to a reduction in confining pressure. when overlying layers are eroded away, the outer layers expand and separate from the rock body. ex: joints
Joints
fractures in the rock caused by expansion or rock, contraction of rock or cracking of rocks by mountain building forces.
salt crystal growth
similar to frost wedging but instead of freeing water, salt crystals get inside and grow. occurs at seashores with a lot of sea spray.
biological activity
disintegration resulting from plants and animals
chemical weathering
breaks down rock components an the internal structure of minerals. water is usually involved
oxidation, dissolution, hydrolysis, spheroidal weathering
oxidation
oxygen dissolved in water will cause oxidation which weakens materials with iron in them.
dissolution
process by which carbonic acid in the water dissolves rocks such as limestone
hydrolysis
carbonic acid reacts with feldspar and breaks it down to produce clay
spheroidal weathering
causes physical changes by rounding corners.
forms when angular rock is chemically weathered as water enters joints
differential weathering
rocks do not weather uniformly due to regional and local factors. an important factor is rock composition.
regolith
rock and mineral fragments produced by weathering
soil
a combination of mineral and organic matter, water, and air.
50% is made of disintegrated rock and minerals plus Humus
50% is made of pore spaces between solid particles where nutrient water and air cirulate
factors controlling soil formation
parent material time climate plants and animals slope
parent material
residue soil, parent material is the underlaying bedrock
transport soil, forms in a place on parent material that has been carried from elsewhere and deposited
Time
amount of time for soil formation varies for different soils depending on geological and climate conditions.
it can take 80-400 years for .5in of soil
climate
most influential control of soil formation
key factors are temperature and percipitaion
plants and animals
organisms influence the soils physical and chemical properties.
also furnish organic matter to the soil
slope
steep slopes often have poorly developed soils
soil profile
soil forming processes operate from the surface downward.
vertical differences are called horizons- zones or layers of soil
-O horizon, A Horizon, E Horizon, B Horizon, C Horizon
