Chapter 13Chapter 13

Introduction to LithosphereIntroduction to Lithosphere

IntroductionIntroductionto Landform Studyto Landform Study

• The Unknown Interior (deepest mine shaft only 2.4 miles deep)

• Composition of the Crust

• Critical Concepts

• The Study of Landforms

• Geomorphic Process, Scale, and Pattern

The Unknown InteriorThe Unknown Interior

Earth’s diameter 8000 miles

• Crust = 5-25 miles

• Mantle = 1800 miles

• Outer Core =1300 miles

• Inner Core = radius 900 miles

CrustCrust

• Outermost shell

• 25 mi deep = continent

• 5 mi deep = ocean

• Base of crust is known as “Moho”

• Altogether crust = < 1% of Earth’s volume

• Circumference Earth = 25,000 miles

MantleMantle

• Extends 1800 miles into interior of Earth

• Constitutes 84% vol. & 66% total weight

• Mantle divided into 3 parts: 1. Lithosphere = mantle + crust = uppermost

2. Asthenosphere = weak sphere = hot rocks

3. Mesosphere = deep mantle = rigid rocks

Outer CoreOuter Core

• Beneath mantle

• Molten liquid

• Extends 3100 miles into interior of Earth

Inner CoreInner Core• Solid and very dense mass

• Radius of 900 miles (from core outward)

Inner and Outer Cores are made of iron/nickel or iron/silicate

Both constitute 15% volume and 32% weight

Earth’s LayersEarth’s Layers

Earth’s InteriorEarth’s Interior

900

The LayersThe Layers

Earth’s Crust and Earth’s Crust and MantleMantle

• Crust is a broad mixture of rock types

• Mantle is largest of 4 shells

• Mantle has 3 sections: 1. crust & lithosphere

2. Aesthenosphere

3. mesosphere

The mesosphere extends downward to 1800 miles

Composition of the CrustComposition of the Crust

• Minerals, Rocks, and Bedrock

• Igneous Rocks

• Sedimentary Rocks

• Metamorphic Rocks

• Rock Classes – uneven distribution of the 3 classes

MineralsMinerals

Naturally occurring minerals, which contribute to the soil content

FYI: Man made mineralsFYI: Man made minerals

MineralsMinerals•natural compounds formed through geological processes

•"mineral" encompasses not only the material's chemical composition but also the mineral structures

•range in composition from pure elements and simple salts to very complex silicates

BedrockBedrock

• Solid rock at surface is outcrop

• Most is buried beneath sediments

• Sedimentary rock composes most of lithosphere

The solid rock that underlies all soil or other loose material

The rock material that breaks down to eventually form soil.

Igneous RockIgneous Rock

The original rock

It all started here

Extrusive - intrusive

Rock formed when molten (melted) materials harden

Extrusive IgneousExtrusive Igneous Intrusive Intrusive IgneousIgneous

When lava reaches the surface of the Earth through volcanoes or through great fissures, the rocks that are formed from the lava cooling and hardening are called extrusive igneous rocks

Millions and even billions of years ago molten rock was cooling and thus hardening into igneous rocks deep under the surface of the Earth. These rocks are now visible because mountain building has thrust them upward and erosion has removed the softer rocks exposing the much harder igneous rocks. These are called intrusive igneous rocks

Extrusive IgneousExtrusive Igneous

Intrusive IgneousIntrusive Igneous

Breaks surface as lava and then cools and hardens

Magma cools and hardens below surface and then is exposed above surface by mountain building

Sedimentary RockSedimentary RockConsolidation of deposited particlesConsolidation of deposited particles

formed by the hardening of material deposited in some process

most commonly sandstone, shale, and limestone

Sedimentary rocks are formed from the breaking apart of other rocks (igneous, metamorphic, or sedimentary rocks) and the cementation, compaction and recrystallization of these broken pieces of rock.

Formation of Sedimentary Formation of Sedimentary RocksRocks

Compaction Cementation

Sedimentary rocks are formed in two ways:

1. by pressing together or compacting loose particles which have been deposited on land or in water bodies such as seas or lakes. These loose particles are called sediments. 2. by the crystallization of dissolved minerals.

By compacting sedimentsBy compacting sediments

By crystallization By crystallization from dissolved from dissolved mineralsminerals

Sedimentary StrataSedimentary Strata

Metamorphic RocksMetamorphic RocksOriginally igneous/sedimentaryOriginally igneous/sedimentaryChanged by heat/pressureChanged by heat/pressure

Metamorphic rocks are sedimentary or igneous rocks that have been altered by heat and/or pressure. As they are derived from previously existing igneous, sedimentary or even metamorphic rock, their appearance is variable. They are identified by the types of minerals they contain and their texture

FoliationFoliationLayering formed as a consequence of the alignment of mineral

grains, or of compositional banding in a metamorphic rock.

The Rock CycleThe Rock Cycle

Distribution of Rock ClassesDistribution of Rock Classes

GeologicTime

Figure 13-18

Geomorphic ProcessesGeomorphic Processes