Geog 1011 Exam 2

endogenic system

the internal processes that build the landscape and topographic relief, includes tectonic processes

exogenic system

external processes that tear down topography, includes erosion and mass movement

landscapes

 result from the interaction between processes that build up topography and those that rip it down

topography

arrangement of natural and artificial physical features of an area

weathering

interacting  physical, chemical and biological processes that cause disintegration or breakdown of rock on the surface

Is there generally movement involved in weathering?

No

Is there generally movement involved in erosion?

Yes

Bedrock

the parent rock from which weathered regolith and soils develop (unweathered, unaltered material)

Regolith

broken up rock typically found right above (surface) of bedrock, undergoes continual weathering

Soil (formation)

formed from weathered regolith

Physical/Mechanical Weathering

*no change in the chemical composition*, just disintegration into smaller pieces

Exfoliation (PW)

igneous rocks formed underground that expand horizontally above ground when pressure is removed and create fractures parallel to the surface

Thermal Expansion and Contraction (PW)

Rocks at surface are subject to changes in temperature, causing rock and soil to expand and contract, creating cracks and sometimes breaks

Frost Action (PW)

Driven by water migration toward ice lenses in rock, force of slowly moving water in colder area breaks rock

Volumetric Expansion (PW)

water seeps into cracks, fractures rock, freezes and expands, wedges apart the rock. With repeated freeze/thaw cycles, rock breaks into pieces

Salt-Crystal Growth (PW)

Dry weather draws moisture to the surface of rocks in arid climates, water evaporates and dissolved minerals (like salt) in the water form crystals that grow over time and can break rocks

Vegetation (PW)

Roots enter crevasses and break rocks apart

Tree Throw

root plate from tree is left behind, roots, rocks and sediments are forced from the ground

Does physical weathering speed up chemical weathering?

Yes, it creates a greater surface area for faster chemical weathering to occur.

Solana

green eyes, little ears

Sirius

super big yellow eyes

Chemical Weathering

the decomposition and decay of minerals in rock due to chemical alterations of those minerals

Key agent of chemical weathering

Water, it can dissolve at least 57 natural elements and their compounds

Hydration (CW)

the absorption of water into the mineral structure of a rock. Can change the structure of the rock, causing swelling and expansion

Hydrolysis (CW)

Silicate materials chemically react with water and produce different compounds

granular disintegration (CW)

Conversion between compounds causes interlocking crystal networks to break down, and they get super crumbly

Oxidation (CW)

certain metallic elements combine with oxygen to form oxides, changes the crystal structure of minerals. These rocks become weaker, and more prone to more physical and chemical weathering

Dissolution of carbonates

This occurs when a mineral dissolves into a solution due to elevated pressures

Karst Topography

occurs when water picks up carbon dioxide from the atmosphere and ground, forms carbonic acid, and results in chemical weathering that can cause caves, sinkholes, cliffs and steep-sided hills called towers

Why is chemical weathering important?

It’s important for agriculture, it releases nutrients from rocks that goes into the soil and water, releases potassium and phosphorus, increases water holding capacity in soils, and consumes CO2 from the atmosphere

What type of weathering is dominant in dryer, cooler climates?

Physical Weathering

What type of weather dominates in wetter, warmer climates?

Chemical Weathering

What factors influence weathering?

Character of the bedrock, climatic elements, aspect, vegetation

Aspect

Weathering on slopes facing north, south, east and west. The aspect effects exposure from the sun, and is especially noticeable at middle or higher latitudes.

How does vegetation impact weathering?

Vegetation can protect rocks from raindrop impacts, stabilizes soil reducing erosion, but can also destroy rock by roots entering rock and cracking it or can destroy rock as a result of organic acids from the tree root.

4 main components of soil

Water, air, organic matter, solid mineral particles

Pedon

hexagonal columns from the surface to the bedrock, basic sampling unit for soil surveys

Soil Horizon R

consists of consolidated rock, usually has little evidence of weathering

Soil Horizon C

weathered bedrock (regolith) below the zone of greatest soil and biological activity

Soil Horizon O

contains organic matter, main accumulation of dead plant and animal material (humus), microbes and other living creates, found above the mineral soil. Not found in every soil.

Soil Horizon A

The topmost mineral layer, darker color, some organic material

Soil Horizon E

zone of maximum leaching of minerals, washing out or eluviation by water. lighter color than horizon A (less organic material)

Soil Horizon B

Accumulation or illuviation of minerals from washing in. Parent material is no longer discernible

Soil Color

helps indicate the composition and chemical makeup of the soil

soil structure

the shape of soil peds (the smallest natural clump or cluster of particles in the soil) determines structure type. Could be crumbly, granular, platy, maddish or blocky

Acidic Soils

contains and excess of hydrogen atoms, deficient in calcium, magnesium, potassium or sodium. These soils are bad for crops, but can be treated with powdered limestone or chalk

Alkaline/Basic Soils

Excess hydrogen atoms, high in calcium, magnesium, potassium, or sodium. Good for most groups because of plentiful nutrients

Soil Porosity

refers to the amount of pores, or open spaces, between soil particles

Primary porosity

a function of the pore size of the material itself

secondary porosity

results of biological, chemical and physical processes altering material

Hans Jenny

Soil scientist and UC Berkely. Sees soil as an open system, with properties that are functionally related. Developed CLORPT Equation

CLORPT

Refers to how soils are formed. Stands for: Climate, Organic material, Relief, Parent Material, Time

Effect of humans on soil erosion and degradation

Humans increase erosion 10-40 times its natural rate

Types of soil moisture

Hygroscopic Water, Capillary Water, Gravitational Water

Hydroscopic Water

bonds to soil particles, not available for plant use

Wilting Point

the point where all water is hygroscopic, meaning there isn’t any water for plants

capillary water

water held in soil pores against the fore of gravity. The only type available for plant use

reaching field capacity

the point where water is no longer being drained, the max amount of water held by soil after excess water drains away

gravitational water

water that drains through the soil by the force of gravity, not available for plant use

Macropores

large soil pores that drain freely by gravity over time when water is added

Why does clay have such a high wilting point?

Clay has a small grain size, more surface area for hydrogen bonding, more hygroscopic water and the highest wilting point

A lower wilting point is the result of

a larger grain/pore size, making it easier for water to drain out

Permeability

the ease at which a fluid flows through a material. soil with larger pores are more permeable

Law of Conservation of Mass

Matter cannot be created or destroy, it is converted to other forms

Importance of the carbon cycle

The amount of CO2 in our atmosphere plays a critical role in our landscape. A rise in CO2 increases the greenhouse effect and warms the earth

Geologic Inorganic Carbon Cycle

The transfer of inorganic carbon between the atmosphere and carbonate rocks. It takes a long time on the geologic scale, and can be caused by chemical weathering, metamorphism and volcanism

Mount Pinatubo Eruption - 1991

Part of Pacific Ring of Fire, one of the largest explosions in the 20th, released 3 cubic miles of material: ash, magma, etc high up into the atmosphere

How do volcanoes compare to humans?

The amount of emissions from humans in 2015 was equal to 646 Mt Pinatubo eruptions

Short Term Organic Carbon Cycle

Transfers carbon between the atmosphere, living biomass and soils

Photosynthesis

Converts CO2 to organic matter

Respiration

Release of CO2 in the presence of oxygen

Fermentation

Release of CO2 without the presence of oxygen

Oxidation of Methane

Methane combines with oxygen to form CO2 in the atmosphere

Keeling Curve

a graph that shows the ongoing change in the concentration of carbon dioxide in Earth’s atmosphere

1/4th of all human related CO2 emissions is due to

agriculture

younger plants

need more CO2 in order to grow. As a plant ages, it requires less CO2

How can we slow down the build up of CO2?

Reducing CO2 released from fossil fuels, increasing carbon stored in vegetation, increasing carbon stored in soils

how has agriculture lead to increase CO2?

deforestation and the burning of plants and trees to create space for crops all increases CO2. converting land to agriculture also reduces soil carbon storage.

Why is bare ground a problem?

Causes greater runoff, higher evaporation, more extreme temperatures, reduced plant growth, reduced carbon storage in soil

Desertification

land degradation/destruction of the biological potential of the land in arid, semi arid and dry sub-humid areas.

Storage of carbon in soil is reduced by

warmer temperatures, increased erosion, land degradation, deforestation, desertification

Permafrost

Soil that remains continuously frozen year round. When it melts, it releases CO2 into the atmosphere and increases surface temperatures

Is mass wasting an endogenic or exogenic process?

Exogenic

Mass Wasting

the movement of mass/material down slope under the influence of gravity

How does weathering effect mass wasting?

weathering weakens rocks and breaks them into smaller pieces which are more easily transported

Dynamic Equilibrium

a state at which erosion of rock and land is countered by an equal deposit of rock or land, resulting in no change to the geomorphology of a place

driving forces

encourage movement

resisting force

slows/stops movement

weight

force exerted on an object by gravity (force = mass \* gravitational acceleration \[9.8 m/s^2\])

what three forces resist downslope movement?

normal force, cohesion, internal friction

cohesion

causes increase in resisting forces when grains are packed or cemented together

Internal Friction

a measure of frictional strength, resistance to space between mineral grains, in loose material, friction angle is close to angle of repose

Angle of repose

the steepest angle that loose, dry material can collect without cohesion. due to grain on grain friction

normal force

exerted on a surface at a particular angle, uses Fn = W cos (angle), can be reduced through water addition

What are the four main types of mass wasting?

falls, landslides, flows and creeps

Falls (mass wasting)

occurs in both rocks and soils, fast moving, materials fall through the air. Happens in dry conditions

Talus slope (mass wasting)

A type of fall where individual pieces fall independently

Landslides

a sudden movement of cohesive mass of regolith or bedrock that is not fully saturated with moisture, large amount of simultaneously falling rock at a range of speeds

Slides/Slumps

These occur where clay rich materials are exposed on steep slopes, causes downward movement of block material down a surface/curve

Rotational slides

type of landslide that occurs in a turning movement on a curved slip surface