Download - 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