Earth's Surface Processes: Weathering & Erosion

• External processes on Earth's surface constantly transform solid rock into sediment.
• This process is essential for the rock cycle.

Weathering and Soil

• Weathering is the physical disintegration and chemical alteration of rocks on or near Earth's surface.
• Weathering breaks down solid rock into smaller fragments and new chemical compounds.

Gravitational Processes

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

Erosion

• The physical removal of material from one location to another by dynamic agents like water, wind, or ice.
• Erosion wears down rocks and transports the resulting fragments to new locations, eventually to be deposited as sediments.
• These processes are powered by solar energy and are crucial in shaping Earth's physical landscape.
• The landscape constantly changes as mountains erode and lakes fill with sediment.

Mechanical Weathering

• Involves the physical fragmentation of rocks into smaller pieces without changing their chemical composition.

Ice Fragmentation (Frost Wedging)

• Occurs when water penetrates rock cracks, freezes, expands, and breaks the rock into angular fragments.
• This process is common in mountainous regions where temperatures fluctuate around the freezing point.

Decompression

• Happens when deeply buried igneous rocks are exposed at the surface due to erosion.
• Reduced pressure causes outer layers of the rock to expand and break off in concentric slabs, forming exfoliation domes.

Thermal Expansion

• Diurnal temperature changes, especially in deserts, cause the rock to expand and contract. With time this can weaken and fracture the rock.

Biological Activity

• Plant roots can penetrate rock cracks and break the rocks as they grow. Burrowing animals can also break down rocks by moving material to the surface, where it can be easily eroded.

Chemical Weathering

• Transformation of rocks through chemical reactions.
• Chemical weathering decomposes rocks through chemical reactions, transforming them into new substances or releasing them into the surrounding environment.

Dissolution

• The simplest chemical weathering process where certain minerals like halite (common salt) dissolve in water.
• Water, being a polar solvent surrounds and separates the ions of minerals, leading them into an aqueous solution.

Oxidation

• Occurs when oxygen combines with minerals rich in iron.
• This process forms iron oxides like hematite (Fe2O3).
• Iron loses electrons & combines with oxygen, causing the decomposition of ferromagnesian minerals like olivine and hornblende.
• Oxidation is similar to how metallic iron rusts and forms rust (iron oxide).

Hydrolysis

• Involves the reaction of minerals with water, especially when containing dissolved acids like carbonic acid (H2CO3), formed from dissolved carbon dioxide in water.
• Hydrogen ions (H+) replace other ions in the mineral structure, decomposing it and forming clay minerals and stable products on the surface.

Formation of Clay Minerals

• A common result of chemical weathering is the formation of clay minerals from the decomposition of silicate minerals, like feldspars.
• Clay minerals are stable products on Earth's surface and an important part of the soil.

Leaching

• The process where water percolates through soil and rocks dissolves & transports soluble ions and minerals. Less-soluble materials are left behind.

Relationship between Chemical Weathering and Erosion

• Chemical weathering and erosion are related, working together to decompose & transport rocky materials.

Preparation of Material

• Chemical weathering decomposes minerals in rocks, transforming them into stable and soluble compounds on the surface.
• This process generates materials easily transported by erosive agents.
• Minerals that becomes soluble can be carried away by water.

Rock Weakening

• Through hydrolysis, oxidation, and dissolution, chemical weathering weakens rock structures. After weakening, these rocks are fragmented and removed by physical erosion through water, wind, or ice.

Material Movement

• Products of chemical weathering, like clay minerals and iron oxides, are easily transported by rivers, wind, and ice masses.
• Ions and soluble compounds can also be carried by groundwater and river systems, contributing to the nutrient cycle and sedimentation in new locations.

Continuous Cycle

• Erosion removes loose and altered products of chemical weathering, transporting them to new locations where they may undergo further chemical weathering in their new environment.

Factors Affecting Weathering

• Influence how and how quickly rocks weather.

Rock Characteristics

• The minerals present in a rock influence the rate and manner of weathering.

Mineral Composition

• Minerals like calcite are soluble in acidic water and decompose quickly. Silicates like quartz are more resistant to chemical weathering.

Fracturing and Porosity

• Rocks with fractures or pores allow water and weathering agents to enter and accelerate the weathering process. Natural fractures (joints) aid this process.

Climate

• The climate is essential to what will erode the rock.

Temperature

• Temperature fluctuations lead to expansion and contraction in rocks, causing fracturing.
• In cold climates, water freezes & thaws (frost wedging) in rock cracks, and this can be an important factor.

Humidity

• Water is needed for chemical weathering. Areas with high humidity show quicker rates of chemical weather because of the readily available water.

Precipitation

• Acid Rain also containing acids accelerates mineral dissolution and hydrolysis.

Topography

• Refers to the gradient or angle of land.

Slope

• Steep slopes help the water run down quicker limiting water interaction times, vs flat grounds.

Orientation

• Directions of the rocks relative the the sun or shadow influence humidity and temperature rates.

Vegetation and Biological Activity

• Roots can fracture rocks adding organic compounds that help with chemical weathering.

Plants

• The roots fracture rocks, and add organic components that help with chemical weathering.

Microorganisms

• Fungis and bacteria help break materiel down the speeding the process up.

Burrowing

• Animals will expose rocks to speed up the weathering components.

Time

• Refers to how long factors act open rocks.

Duration

• The longer a rock sits the more it breaks down on the surface.

Soil

• Is what helps to grow any kind of plants

Definition

• It is mineral, organic, air, that helps sustains plan growth.

Formation

• It is a few interacting factors.

Factors

• A key is parent rock provides the mineral to from it but also weather elements, water acidity

Time

• The amount of passing has a key to its forming the more deeply divided it becomes.

Climate

• This affects temperatures and precipitating to how soils form, hot helps make them deep.

Plants

• The fauna and the fauna can help with organic enrichment .

Organisms

• They also break down the organic parts to provide nutrients.
• Slopes can help erode thin soils vs low lands for thicker soils

Horizons of Soil

• They provide various layers.

Level O

• Contains leaves and vegetation organic top layer.

Level A

• Is a humus mix top layer.

Level E

• Is materials and soluable fines are found in.

Level B

• Zone where leached soils move to

Level C

• It contains some signs of what the parent material as that original rocky layer.

Classifying

• We use systems that classify physical and chemical components.

Definition

• Based of what the soil as in profile what does the physics show

Classes and Characteristics

• Alfisols are found under foressts high in iron an aluminum, and balanced in wet vs dry
• Andisols as volcanic ash in active are high is water retain
• Aridisols, in dry areas can retain lots of salt and calcium Entisols, vary widly

Gelisols

• Bery cold with permafrost and freezing slows this
• Histosols are organic rich in the wetlands with water
• Inceptisols are young in wet climates witj bogs
• Mullisols are dark in grasslands high in calcium and more.

Oxisols are high in Aluminum

• Spodosols are arenous soil, and have trees
• Ultisols are clay heavy and not rich
• Vertisols shring rich soils that are a problem for infrastructure.
• They help understand uses and properties

Soil Erosion

• It is the movement of water by wind.

Natural erosion

• is in rocks moving

Activities with Humans

• It may be speed it up which creates soil loss naturally by wind and water.
• When rain falls the rain helps kick up particles to wash them away as sheet wash
• Formation is where they go into new streams .
• Wind then takes particles to new locations.

Erosion speeds

• Rates depends of coverages of vegetations such deforestation can speed this up.
• Topsoil loss causes agriculture to be less potent, can be swept to water which can cause chemical damage
• Conservation method
• To combat agriculture run lines alomg contours of lands for drainage.
• Rotation helps reduce

Sedimentary Rock

• Weathering can break rocks or existing rocks which then get deposited by elements for compaction

Formation of deposits.

• The rocks get weathered down

Deposition

• Is when rocks particles get decomposed in water, etc. This can occur by lakes and more.
• With increasing amounts of sediments compacted.

Accumulations

• The water will then be able to fill these as the compact to form
• Mineral precipitate when rocks forming into solid types.

Rock Type Importance

• The rocks can give indications of earth formations.

Distribution

• 5km volume

Geo

• Formations and records

value

• Sedimentary rocks has coal and others

Sediment to Rock

• Sedimentary forms can give indications of chemical bio logs that can turn them solid And are affected by temperature with recrystalizing of minerals to make stable rock.

Lithification

• The process of consolidation, the sediment will over lap and make porous types..

Cementation

• Happens when waters flow with rocks together. These cause consolidation
• It causes steady changes to soil to structures..

Geological Evidence

• Sediment records

Sedimentary Type

• Can be detritus

Clastic rock composes

• Most rock components such as clay
• Arenites have sands that are well sorted out in deserts and such
• COngleromerate is course

Chemical Rock

• When mineral precipitate out this happens, organic bio activity.

Limestone has calcium

• Dolomite has mineral component

Sandstone is slica

Other Rock Types

• These can from evaporation and is in gypsum and more
• They have to be mineral specific
• They can tell what happened in the past what did the environment do to what part of the landscape, wind and currents.

Continental

• Erosion and deposition are dominated

marine

• Shallow and deep are the types

Transitional

• Shores beaches are

Land forms from types

• The ones transitional are at edges of earth
• Low lands from bars and ridges

Facies Sedimentation

• Shows what sediments are like how much what types of material in what environment.. these pass gradually with diff condition

Sedimentary structures

• The rocks have various structures.

Bedding or layering

• The bedding as successive sediment deposits

Cross bedding deposits

• Occur in horizontal locations.

Graded bedding

• Has sediment change top to bottom grading

Ripple marks

• Wind causes types
• Current types cause assymetry
• Desiccation is at lake beds.

Infill structure

• They will have sediment mixing action

Rock metamorphosis

• It is a changing structure form of the rock with chemistry. This depends on pressure temps.

The keys of it are the factors of metamorphosis

• It is how heat helps which can change or crystalize

Pressure differential

• Aims to control different stress and volume.
• Fluids can be easily moved for them to form.

Grades

• Can differ for high rock grades

Contact thermo

• Happens intrsively Hydro thermal changes chemistry
• This impacts sediments an creates new rock material

Metamorphic

• Many factors have an impact

Import

• Heat provides energy for rock formulation changes
• It heats them up allowing dissolutions to re create. this allows them to become elevated.

Pressure

• Causes the rock to reduce volume uniform, they get crushed in pressure the fluids allows reactions

Meta Morph is them

Portolito

• The mother of the materials. The shale goes to slate
• Mefic is magneisms in those minerals.

Mineral is key

• Hardness is cuatz then it doesn't react, marble will react. Textures will vary what morph the text is with sizes. What is described is shape how they lay down Foliating how flat minerals lay and align, they shimmer and the grades.

Gneissic banding

• It how colors get layered in the rock The minerals can be all different this affects porfido, blastica rock

Rock shapes vary for rock to not have layers also

• No layers or crystal types and quartz ones is quartz like cuorizite
• Textures

Folding, the grains change

• Can then take preferential rotations

Most crystals are on the non folia

• Will show what the original material was like

Sizzz and the other one

• Is easy to find the rock, and some minerals lay different color
• Slate and phyllis exist.

Genes can be schist

• There are then nonfolaided such as marble. The contacts then occur and form.

The zone then forms and the change

• They come from the same thing

Grade of the different rocks change, the textures

Explore Earth's surface processes like weathering, gravitational movements, and erosion that transform rocks into sediment. Weathering disintegrates rocks physically and alters them chemically. Erosion removes and transports material, reshaping the landscape through water, wind, and ice, driven by solar energy.