weathering and soil formation. ayers rock… another view

Approximately how far away from Ayers Rock is the closest McDonalds restaurant?

465 km (289 miles). The closest McDonalds is in Alice Springs. 22 km to Yulara then another 443 km to Alice Springs

Coach Holmes indicator for,“How far out in the boonies are we?”Distance from civilization.

Essential Question:NCSCOS: EEn.2.1.3Explain how natural actions such as

weathering, erosion(wind, water and gravity), and soil formation affect the Earth’s surface.

E.Q. - What are the mechanisms of weathering

Objectives and GoalsRecall that soil is the result of weathering of

rocks and includes weathered particles: sand, silt and clay.

Explain differences in chemical and physical weathering how weathering rates are affected by a variety of factors including climate, topography and rock composition.

Writing:In your journals:

Give your definition of weathering.

Part I WeatheringThe breaking down of rocks and other materials on the Earth’s surface is called weathering. A slow, continuous process, it affects all substances exposed to the atmosphere.

Types of Weathering

Mechanical WeatheringWhen the forces of weathering break rocks into smaller pieces but do not change the chemical makeup of the rocks, the process is called mechanical weathering. During mechanical weathering, rocks are broken into different shapes and smaller pieces. At the beginning the edges are jagged, as weathering continues, they become round.

Causes of Mechanical WeatheringMust involve motion or movement

Temperature / ExfoliationFrost action / Ice wedgingOrganic activity / Root PryGravity / Rolling down hillAbrasion / Sand blastingGlacier / Till

TemperatureRocks can be broken apart by changes in temperature. As rocks are heat up in the sun during the day, the outside of the rock expands. The inside of the rocks remain cool and do not expand. When the air temperature drops at night, the outside of the rock cools and contracts. This continuing cycle causes particles to break off. This is called exfoliation.

Rock Exfoliates

Study the figure and answer the questions below in your notebook.

a Are the changes in temperature gradual or rapid?b In which regions do these fluctuating temperatures often occur?c Where are the points of weakness in the rock?

Frost ActionUnlike most liquids, water expands when it

freezes. The repeated freezing and melting of water, called frost action, is another cause of mechanical weathering. When water freezes in cracks in the rocks, it expands, making the crack larger.In time, this causes the rock to break into pieces.

Ice Wedging / Frost Action

.Study figure and answer the questions below in your notebook

a Where is the rainwater going?b What happens when temperatures fall below 0°C?c Why has the crack widened?d What effect will this have on the rock?e Which process does this flow chart illustrate?

Organic ActivityPlants and animals can cause mechanical weathering. The roots of plants sometimes loosens rock material. A plant growing in a crack can make the crack larger as the root spread out. This is known as root-pry. It is organic since this activity is caused by living things.

Study the figure and answer the questions below in your notebook.

a What happens to the crack as the roots get bigger?b What kind of weathering is this?c What kind of weathering does this process cause?d The decaying tree will provide…

GravityGravity is another agent of mechanical weathering. Sometimes gravity pulls loosened rocks down mountain cliffs in a landslide. A landslide is a large movement of loose rocks and soil, know as MASS MOVEMENT. As the rocks fall, they collide with one another and break into smaller pieces. Falling rocks usually occur in areas where a road has been cut through, leaving cliffs on both sides.

AbrasionWind-blown sand causes mechanical weathering . Abrasion is the wearing away of rocks by solid particles carried by wind, water or other forces. In desert regions or at the beach, the wind easily picks up and moves sand. The sharp edges of the sand particles scrape off pieces of exposed rocks. Running water also carries loose rocks which scrape against each other and break.

Sandblasting Arthttp://www.youtube.com/watch?v=apjYHZKZV6k&safety_mode=true&persist_safety_mode=1

Chemical Weathering When the chemical makeup of the rocks is changed it is called chemical weathering. During chemical weathering, changes occur in the mineral composition of rocks. Minerals can be added, removed or broken down (decomposed). Many substances react chemically with rocks to break them down.

Types of Chemical WeatheringThe chemical composition must be changed

Water /dissolvingOxidation / RustingCarbonation / Acid Rain weakSulfuric acid / Acid Rain strongPlant acids / Mosses and lichens

WaterMost chemical weathering is caused by water and carbon dioxide. Water can dissolve most of the mineral that hold rocks together. Rocks that dissolve in water are said to be soluble. Water can form acids when it mixes with certain gases in the atmosphere to speed up the decomposition of rocks. Water can also combine with a mineral to form a new mineral.

Evaporites

Our State (Magazine)Linville Caverns Video

https://www.youtube.com/watch?v=242YYeGdid4

OxidationChemical weathering is also caused by oxidation. Oxidation is the process in which oxygen chemically combines with another substance. The result of oxidation is the formation of an entirely different substance. Iron in rocks combines with oxygen in the air to form iron oxide, or rust.

CarbonationWhen carbon dioxide dissolves in

water, a weak acid called carbonic acid is formed. When carbonic acid reacts chemically with other substance, the process of carbonation occurs. In nature, carbonic acid is formed when carbon dioxide in the air dissolves in rain. This acid rain falls to the ground and sinks into the soil. It decomposes feldspar and limestone.

Study the figure and answer the questions below in your notebook.

a What kind of weathering is this?b How does this kind of weathering affect the rock?c Which climates speed up this kind of weathering?

Sulfuric AcidThe air in certain areas is polluted

with sulfur oxides. Sulfur oxides are a byproduct of the burning of coal as a source of energy. These compounds dissolve in rainwater to form sulfuric acid. Rain that contains sulfuric acid is one type of acid rain. It is much stronger than carbonic acid. Sulfuric acid corrodes rocks, metals and other materials quickly.

Plant AcidsPlants produce weak acids that

dissolve certain minerals in rocks. Mosses and lichens produce weak acids that dissolve some of the minerals in the rocks they grow on in areas of PERMAFROST / Polar Climates. Gradually the rocks break into smaller pieces. They are important in the formation of soil.

Rate of WeatheringThe composition of the rockThe amount of time that the rock is exposed on the Earth’s surface

The amount of exposed surface on a rock

ClimateRelief / Topography (Height)

Rate of Getting WetCheck your understanding of weathering rates.

With a partner list five different ways that your clothes become saturated with rain more and/or faster. Then compare that list with your notes on the rates of weathering

Rate of Weathering Graph

Composition of RocksTwo different types of rocks in the same climate can weather differently, depending on the minerals that make up each rock type. If a rock resist weathering, the rock is called a STABLE ROCK. The stability of a rock can vary depending on the climate in which the rock is found. Limestone is stable in a dry climate but not in a wet climate.

Amount of Time of ExposureThe amount of time that rock is exposed on the Earth’s surface also affects its rate of weathering. A very old rock that has not been exposed to the forces of weathering can remain almost unchanged. If a newly formed rock is deposited on the Earth’s surface it will begin to weather right away.

Vs.

Which Is Older????

The Amount of Exposed SurfaceThe amount of exposed surface area on a rock also affects its rate of weathering. As rocks are broken down into many small pieces, more rock surfaces are exposed and more weathering takes place. In rocks that contain many joints or cracks, various chemicals easily come into contact with the rock surfaces and break them down.

Vs.

Which Dome is more exposed???

Chimney Tops… G.S.M.N.P.

ClimateCold and/or dry climates favor

physical weathering. Arctic/Polar

Warm and wet climates favor chemical weathering. Tropical

Frost action works best in areas where the temperature fluctuates wildly. Temperate Climates

Part 2

Part II Erosion and DepositionEssential Question:

Compare erosion by water, wind, ice, and gravity and the effect on various landforms

What Caused This?What Caused This?

What is Erosion?What is Erosion?Erosion – Erosion – the moving of rock material the moving of rock material from one place to a new locationfrom one place to a new locationFor erosion to occur For erosion to occur three processes three processes

must take place: must take place: detachment of detachment of particles, lifting them, and particles, lifting them, and transporting themtransporting them

Many agents of erosion - flowing water, Many agents of erosion - flowing water, moving ice, waves, gravity, or windmoving ice, waves, gravity, or wind

Sand, silt and clay Sand, silt and clay consists of small consists of small pieces of rock that have been weathered pieces of rock that have been weathered from a parent rock, eroded, and deposited from a parent rock, eroded, and deposited somewhere elsesomewhere else

What Is Wind Erosion?What Is Wind Erosion?WindWind - - responsible for wearing away responsible for wearing away

rocks and creating great deserts like the rocks and creating great deserts like the Sahara Desert and GobiSahara Desert and GobiMost effective in moving loose materialMost effective in moving loose material Two main effects: (1) Wind causes small Two main effects: (1) Wind causes small

particles to be lifted and moved away. (2) particles to be lifted and moved away. (2) Suspended particles may impact on solid Suspended particles may impact on solid objects causing weathering by abrasion objects causing weathering by abrasion (rubbing/blasting).(rubbing/blasting).

Occurs in areas where there is not enough Occurs in areas where there is not enough rainfall to support vegetationrainfall to support vegetation

What Is Water Erosion?What Is Water Erosion?Water - most influential force in erosion

Ability to move materials from one location to another over long distances

The faster water moves in streams the larger objects it can pick up and transport. Known as STREAM LOAD

Responsible for wearing away of rocks in rivers, lakes, and the oceans

What Is Wave Erosion?What Is Wave Erosion?Waves - relentless pounding

Erodes the softer, weaker parts of the rock first, leaving harder, more resistant rock behind

Can take over 100 years to erode a rock to sand

Energy of waves along with the chemical content of the water erodes the rock off the coastline

What Is Gravitational Erosion?Mass movement - downward movement

of rock and sediments, mainly due to the force of gravity. Moves material from higher elevations to lower

elevations where streams and glaciers can pick up the material and move it to lower elevations

Process is occurring continuously on all slopes, some act very slowly while others occur very suddenly until equilibrium is reached

What Is Glacial Erosion?What Is Glacial Erosion?IceIce - - moves and carries rocks, grinding moves and carries rocks, grinding

the rocks beneath the glacierthe rocks beneath the glacierWeathering Abrasion cuts into the rock under Weathering Abrasion cuts into the rock under

the glacier, smoothing and polishing the rock the glacier, smoothing and polishing the rock surfacesurface

With the same glacial process material is With the same glacial process material is transported to new locations.transported to new locations.

HOMES ???HOMES ???

What is Deposition?What is Deposition?Deposition Deposition -- laying down of sediment laying down of sediment

that has been that has been eroded/transportederoded/transported by a by a medium such as wind, water, waves, medium such as wind, water, waves, gravity or icegravity or ice

Process of erosion stops when the moving Process of erosion stops when the moving particles fall out of the transporting particles fall out of the transporting medium and settle on a surface. medium and settle on a surface. This This settling of eroded material into a new settling of eroded material into a new location is called location is called deposition.deposition.

ObstaclesObstacles, whether natural or man-made, , whether natural or man-made, will often decide where the deposition will often decide where the deposition occurs and the nature of the feature occurs and the nature of the feature formed.formed.

What’s the Difference?WEATHERING - think weather wearing rock

down

EROSION - think of a road and traveling

DEPOSITION – think of depositing money in a bank

Part III Soils“What is Soil ?”

What is Soil?Soil - Soil is a natural body comprised of solids (weathered minerals, rock and decaying organic matter called humus), liquid (water), and gases (air) that occurs on the land surface, occupies space, and is characterized by horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment.

What is Dirt??? Often referred to mistakenly as soil. Dirt is actually unclean matter, especially when it is in contact with a person's clothes, skin or possessions when they are said to become dirty. Common types of dirt include mud, dust and, yes, soil itself. Any unclean substance, such as mud, dust, excrement, etc.; filth

What’s the difference between soil and dirt?

Dirt is what you find under your fingernails. Soil is what you find under your feet.

Think of soil as a thin living skin that covers the land. It goes down into the ground just a short way. Even the most fertile topsoil is only a foot or so deep. Soil is more than rock particles. It includes all the living things and the materials they make or change.

Soil FormationThe weathering of rocks on the Earth’s surface results in the formation of soil.

Soil is formed when rocks are continuously broken down by weathering.

As rocks weather, they break into smaller pieces.

These pieces are broken down into even smaller pieces to form soil.

Importance of SoilThe formation of soil is extremely important to most living organisms.

Plants depend on soil as source of food.

Soil supplies plants with minerals and water needed for growth.

Animals depend indirectly on soil since they eat plants and other animals that eat plants.

Residual Soil; Lives at HomeSometimes soil remains on top of its parent rock, or the rock from which it was formed. This is called residual soil. Residual soil has a composition similar to that of the parent rock it covers.

Transported Soil; ErosionSome soil is removed from the parent rock by water, wind, glaciers and waves. Soil that is moved away from its place of origin is called transported soil. Transported soil can be very different in composition from the rock it covers.

BedrockThe layer of rock beneath the soil is called bedrock. Also Known as Parent Rock

DecayCertain bacteria in the soil cause the decay of dead plants and animals.

This decaying material is called humus. Humus is a dark-colored material that is important for the growth of plants.

Some of the chemicals produced during the process of decay speed up the breakdown of rocks into soil. Acids

Living ThingsLiving things such as moles, earthworms, ants and beetles help to break apart large pieces of soil as they burrow through the ground. The burrows allow water to move rapidly through the soil. The water speeds up the weathering of the underlying rock.

Soil CompositionPieces of weathered rock and organic material, or humus, are the two main ingredients of soil. Organic materials is material that was once living or was formed by the activity of living organisms. Rock particles form more than 80% of soil. Air and water are also present in soil.

Minerals in SoilClay and quartz are the most abundant minerals in soil. Because they are stable, they exist in the greatest quantities. Potassium, phosphorus and the nitrogen compounds called nitrates are important chemicals in soil. They are vital to plant growth.

Pore SpacesAir and water fill the spaces between soil particles. These are called pore spaces. Plants and animals use the water and air in these spaces, as well as the minerals dissolved in water. Pore spaces provide needed oxygen for healthy plant root growth.

Different Compositions of SoilThe composition of soil varies from

place to place. The type of rock broken down by weathering determines the kinds of minerals in the soil. The type of weathering also affects the composition of soil.

Mechanical weathering produces soil with a composition similar to the rock being weathered.

Chemical weathering produces soil with a different composition.

Soil TextureThe type of weathering also affects soil texture. Texture refers to the size of the individual soil particles. Soil particles vary from very small to large. Both mechanical and chemical weathering first breaks rocks into gravel (2-64mm) and then in sand (less than 2mm) and then into silt and finally clay.

Soil HorizonsAs soil forms, it develops separate soil layers called horizons. Each soil horizon is different. A cross section of the soil horizons is called soil profile. A soil profile shows the different layers of soil.

Evolution of Soil Horizons

Topsoil; Root Zone

Parent Rock

New Horizon Classification

Mature SoilSoil that has developed three layers is called mature soil. It takes thousands of years and the proper conditions for soil to develop three layers. The uppermost layer of mature soil is called the A horizon. The A horizon is a dark-colored soil layer in which much activity by living organisms takes place. Bacteria, earthworms and beetles help the decay.

O (Organic) Horizon

This is the organic debris that has recently accumulated on the surface of the soil. It has begun to decompose.

A HorizonThe soil in the A horizon is called topsoil. Topsoil consists mostly of humus and other organic materials. Humus supplies minerals essential for plant growth. Humus is spongy and stores water. It also contains pore space for air and water. Topsoil is the most fertile part of the soil.

E (Eluviation) HorizonThis eluviation (leaching) layer is light in color; this layer is beneath the A Horizon and above the B Horizon. It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips through the soil (in the process of eluviation).

Virgin Soil

Soil that has little or no humus/organic mater incorporated. “B” horizon and below

Soil that is as yet undeveloped

Soil that has not been cultivated before

Virgin soil, when compact and of considerable depth, is a good material to build on, providing the structure is not an extremely lofty or heavy one.

B HorizonWater that soaks into the ground washes some minerals from the A horizon into the second layer of soil, or the B horizon. This process is called leaching. The B horizon is just below the A horizon. The B horizon is also made of clay and some humus. The soil in the B horizon is called subsoil. Subsoil is formed very slowly.

C HorizonThe third layer of soil is called the C horizon. The C horizon consists of partly weathered parent rock. The C horizon extends down to the top of the un-weathered parent rock. The composition of the soil in the C horizon is similar to that of the parent rock.

What are the differences between eluviation and illuviation?

Eluviation is the leaching down or movement of the particles (such as minerals and organic matter) into lower soil horizons. While, Illuviation is the accumulation of those particles in the lower soil horizons.

R(rock) HorizonSolid un-weathered bedrock. Referred to Parent Rock. It is either…Permeable – allowing most substance to pass or flow in and out

Semipermeable - allowing some substances to pass

Impermeable or Nonpermeable – materials cannot pass through

Immature Soil In some places, the upper layers of soil are removed and the rocks below the soil are exposed. The weathering process then forms new soil from the exposed rocks. This recently formed soil is immature because there has not been enough time for all three soil layers to form. The soil in the northern regions where glacial erosion has taken place, is immature soil.

Formation of SoilThere are several factors that determine whether three layers of soil will form.TimeClimateType of rock / Parent RockSurface features of the region

TimeTime is one of the most important factors in soil formation. The longer a rock is exposed to the forces of weathering, the more it is broken down. Mature soil is formed if all three layers have had time to develop.

ClimateClimate is another important factor in the formation of soil. In areas with heavy rainfall and warm temperatures, weathering takes place more rapidly. Heavy rainfall may wash much of the topsoil away. Since Organisms are more plentiful these areas, the soil is quickly replaced. They speed up the chemical and mechanical weathering of rocks.

Type of RockThe type of rock in an area also affects soil formation. Some rocks do not weather as rapidly as other do. Rocks that do not break down easily do not form soil rapidly. In some climates it takes along time for granite to break down. So soil formation from granite is slow. But sandstone breaks easily and forms soil quickly.

Surface Features of RegionThe surface features of the region also determine the speed at which soil is formed. On very steep slopes, rainwater running off the land erodes the soil and exposes rock to weathering.

Four Soil Formation Processes

GenesisThese processes of soil genesis, operating

under the influence of environmental factors, give us a logical framework for understanding the relationships between particular soils and the landscapes and ecosystems in which they function. This approach is known as internal process modeling. In analyzing these relationships for a given site, ask yourself:

Ask yourself…What are the materials being added to this

soil?

What transformations and translocations are taking place in this profile?

What materials are being removed?

How do climate, organisms, topography, and parent material affect these processes over time?