interlude b

what is weathering?

the physical breakdown (disintegration in place) and chemical alteration (decomposition) of rock at Earth’s surface.

what is erosion?

the physical removal and transportation of such material by mobile agents such as water, wind, ice, humans or gravity.

what is mass wasting?

the transfer of rock and soil downslope under the influence of gravity.

what is frost wedging?

freeze and thaw of water; water expands 9% in volume upon freezing; splits rock apart.

what is exfoliation?

or Unloading: the onion-like peeling of rock surfaces forming concentric slabs.

what is thermal expansion?

varying heat from day to night causes rock to expand and contract forming open cracks or joints.

Joints do not show any movement or offset with them otherwise they would be classified as

faults!

what is biological activity?

tree roots, rodents, & insects dig into the ground to break up soil & rock to eventually cause further physical & chemical reactions.

what is chemical weathering?

Breaks down rock components and internal structures of minerals; causes chemical reactions to occur.

what is the most important chemical agent?

water, h2O

what is dissolution?

Aided by small amounts of naturally occurring carbonic acid: H2O + CO2 = H2CO3 in water to dissolve minerals.

what is oxidation?

Any reaction when electrons are lost from one element and combine with oxygen.
(4Fe + 3O2 = 2Fe2O3 or Hematite)

what is hydrolysis and hydration

The reaction of any substance with water. ✓Hydrogen ion attacks and replaces other metal ions. ✓Causes mineral structure to expand and weaken. ✓Hydrolysis of feldspar forms soft clay minerals: kaolinite.

what factors affect weathering?

Increases surface area, allowing physical &

chemical weathering to be more efficient.

rates of weathering?

Climate/geography:

a) warm & wet climates make for efficient chemical weathering: tropical areas

b) cold & dry/wet climates make for efficient physical weathering: polar areas

c) temperate climates (NYC region) are a mixture of moderate physical & chemical weathering rates.

how is wind an agent of erosion?

blows only the smallest sand and dust particles into piles (sand dunes) or accumulates into low areas (deserts).

how is water and agent fo erosion?

moves all sizes of sediment particles depending upon water velocity: the higher the water velocity, the larger the particle; eventually erodes mountains/carves valleys.

how is ice and agent or erosion?

glaciers move all types and sizes of sediments down slope until the ice melts releasing the sediments.

what is an agent of erosion: gravity?

rapid to slow movement down slope of all types of sediment; mass wasting.

what is an agent of erosion: humans?

un-natural movers of all types of sediment on a large to small scale.

what are different types of mass wasting?

a) Rock Falls: rapid movement of rock or ice.

b) Soil Slumps: rapid to slow movement of soil.

c) Creeps: very slow movement of soil/rock.

d) Slides: very fast movement of soil, ice and rock.
e) Flows: fast movement of water-saturated soil.

landslides

✓ From 2004 and 2023 there were 4,800 fatal landslides, killing ≈ 56,000 people or about 25-50 people/year.

✓ Most caused by construction, mining, and digging operations.

✓ Landslides are the 3rd most leading cause of death derived from earthquake

activity.

who cares about soil?

✓ Soil is the foundation of life on land.
✓ It represents the one of the largest carbon

reservoirs on Earth.

✓ Soil stores twice as much carbon as the atmosphere and vegetation combined.

✓ Soil is vulnerable to degradation via conventional agricultural practices and from

global warming caused by humans.

✓ Effective soil conservation is necessary to sustain food, fuel, and fiber sources to support a

growing human population.

Soil: So What is it?

Soil = combination of mineral & rock fragments, organic matter, water, and air.

✓Rock and mineral fragments (aka regolith) produced by both types of weathering that supports the growth of plants.

✓The ultimate weathering product of rocks in equilibrium with the atmosphere.

✓Humus or organic matter (decayed animal and plant remains) is a small, but essential, component of soil.

what is soils origin?

Parent material: determines what soil type is developed; a granitic rock will produce sandy soil, while a basaltic rock will produce clay-type soil.
A residual soil forms in place from any parent material weathered bedrock.

what is volcanic soil?

Volcanic soil covers 1% of the Earth’s surface but supports 10% of world’s food supply.

Where does this soil originate?

derived from other regions and transported by rivers, floods, or glaciers; 24 billion tons/year transported by rivers to the oceans; Long Island soil.

how does time play a factor in soil formation?

Amount of time for soil formation varies for different soil types depending on geologic and climatic weathering conditions.

➢The more time has passed, the deeper the soil generated.

how does a regions climate play a role?

✓ Most influential control of soil formation.

✓ Key factors are temperature and precipitation.

✓ Presence of plants & animals.

✓ Influence the soil’s physical and chemical properties.

how does topography play a role in soil formation?

Shape & elevation of the land.

✓Steep slopes often have poorly developed soils.

✓Soil usually does not develop on slopes.

✓Optimum terrain is a flat-to-undulating upland surface.

what is o-horizon?

mostly rich in black organic matter or humus with very little mineral matter.

what is a-horizon?

some organic and mineral matter, can be black to brown in color.

what makes up the topsoil

O- and A-horizons make up the topsoil

there is lots of biological activity in these two layers

what is the e-horizon?

Zone of LEaching where chemicals are dissolved out, contains little organic matter, and is light in color.

what is the b-horizon?

Zone of Accumulation of dissolved chemicals from overlying horizons, may contain clay & iron oxide minerals.

what is the c-horizon?

partially decomposed and altered parent or bedrock.

what are some soil problems?

In many regions, soil erosion is much greater than the rate of soil formation.

✓Related to excessive soil erosion; 3 to 5 million acres of farmland soil is lost each year due to erosion.

✓Occasionally soil particles are contaminated with pesticides and other chemicals from illegal industrial disposal and dumping.

what do the natural rates of soil erosion depend on?

1. Soil characteristics

2. Climate type

3. Slope angle

4. Type of vegetation