Earth Science

Earth ScienceEarth Science

Chapter 2 Chapter 2

Weathering & SoilWeathering & Soil

Minerals & RocksMinerals & Rocks Rocks are made up of Minerals.Rocks are made up of Minerals. Minerals are:Minerals are:

– Naturally occurringNaturally occurring– InorganicInorganic– SolidSolid– Definite chemical compositionDefinite chemical composition– Specific Crystalline shapeSpecific Crystalline shape

3 Types of Rocks3 Types of Rocks

IgneousIgneous SedimentarySedimentary MetamorphicMetamorphic

The Rock Cycle

The Rock CycleThe Rock Cycle

Igneous RocksIgneous Rocks – – cooled molten cooled molten materialmaterial

IntrusiveIntrusive – molten material cooled beneath the Earth’s surface – molten material cooled beneath the Earth’s surface– Slow coolingSlow cooling– Large crystalsLarge crystals– GraniteGranite

ExtrusiveExtrusive – molten rock cooled on Earth surface – molten rock cooled on Earth surface– Rapid coolingRapid cooling– Small or no crystalsSmall or no crystals– Obsidian, basaltObsidian, basalt

SedimentarySedimentary – broken pieces – broken pieces from erosion & weatheringfrom erosion & weathering

Formed from sediments being Formed from sediments being compactedcompacted, , cementedcemented or or precipitatedprecipitated from solutions from solutions

Sandstone, limestone, conglomerateSandstone, limestone, conglomerate

Metamorphic Metamorphic – – heat & pressure heat & pressure formedformed

Foliated & nonfoliatedFoliated & nonfoliated– Foliated – layered Foliated – layered

““cooked” in Earth’s interiorcooked” in Earth’s interior– Can change igneous, sedimentary or even previously Can change igneous, sedimentary or even previously

formed metamorphic rocksformed metamorphic rocks– (igneous) (igneous) GraniteGranite GneissGneiss (foliated) (foliated)– (sedimentary) (sedimentary) limestonelimestone marblemarble (nonfoliated) (nonfoliated)

Metamorphic RockMetamorphic Rock

WeatheringWeathering The breaking of rock into smaller & smaller piecesThe breaking of rock into smaller & smaller pieces

– MechanicalMechanical – wind, freezing, abrasion, release of pressure, – wind, freezing, abrasion, release of pressure, plant & animal actionsplant & animal actions

– ChemicalChemical – water dissolves, oxidation (rusting), plants secrete – water dissolves, oxidation (rusting), plants secrete acid, pollution (acid rain)acid, pollution (acid rain)

Affected by the surface area of the rock exposed to the Affected by the surface area of the rock exposed to the weathering processweathering process

Mechanical WeatheringMechanical Weathering

Chemical WeatheringChemical Weathering Alters the chemical makeup of the Alters the chemical makeup of the

rockrock– OxidationOxidation – “rusting”; oxygen reacts – “rusting”; oxygen reacts– HydrolysisHydrolysis – dissolving minerals – dissolving minerals– Carbonic acidCarbonic acid –”acid rain – extra CO –”acid rain – extra CO22 in in

atmosphere mixes w/ Hatmosphere mixes w/ H22O to form a O to form a weak acid.weak acid.

– PlantsPlants – secrete weak acids to break – secrete weak acids to break down rock.down rock.

Soil FormationSoil Formation SoilSoil is the loose, weathered material on

Earth's surface in which plants can grow. It is a mixture of rock particles, minerals, mixture of rock particles, minerals, decayed organics (humus) , air & water.decayed organics (humus) , air & water.

BedrockBedrock is the solid layer of rock beneath the soil.

Soil forms as bedrock is weathered & mixes w/ organics & materials.

As soils form, it develops “layerslayers” called horizonshorizons. Each horizon is named w/ lettersletters (O, A, B & CO, A, B & C) down to the bedrock.

Soil textureSoil texture determined by the sizesize of the particles making up the soil.

Soil TexturesSoil Textures: : Sand, Silt & Sand, Silt & ClayClay

GravelGravel: > 2 mm: > 2 mm SandSand: .05 -2.0 mm: .05 -2.0 mm SiltSilt: .002 - .05 mm: .002 - .05 mm ClayClay: < .002 mm: < .002 mm

Soil w/ equal parts of sand, silt and clay is called a “loam”

Soil HorizonsSoil Horizons Soil HorizonSoil Horizon Names and Names and

Descriptions:Descriptions:OO:: Decaying plants on or near surface Decaying plants on or near surfaceAA:: Top Soil, Organic Rich Top Soil, Organic RichBB:: Subsoil, Most Diverse Horizon and the Subsoil, Most Diverse Horizon and the Horizon with the most sub classificationsHorizon with the most sub classifications

CC:: Weathered/aged parent material Weathered/aged parent material

Life in the SoilLife in the Soil