Introduction to Lithosphere Chapter 13 Introduction to Lithosphere

Introduction to 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 Interior Earth’s diameter 8000 miles Crust = 5-25 miles Mantle = 1800 miles Outer Core =1300 miles Inner Core = radius 900 miles

Crust 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

Mantle Extends 1800 miles into interior of Earth Constitutes 84% vol. & 66% total weight Mantle divided into 3 parts: Lithosphere = mantle + crust = uppermost Asthenosphere = weak sphere = hot rocks Mesosphere = deep mantle = rigid rocks

Outer Core Inner Core Beneath mantle Molten liquid Extends 3100 miles into interior of Earth Inner 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 Layers

Earth’s Interior 900

The Layers

Earth’s Crust and Mantle Crust is a broad mixture of rock types Mantle is largest of 4 shells Mantle has 3 sections: crust & lithosphere Aesthenosphere mesosphere The mesosphere extends downward to 1800 miles

Composition of the Crust Minerals, Rocks, and Bedrock Igneous Rocks Sedimentary Rocks Metamorphic Rocks Rock Classes – uneven distribution of the 3 classes

Naturally occurring minerals, which contribute to the soil content

FYI: Man made minerals

Minerals 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

Bedrock Solid rock at surface is outcrop The solid rock that underlies all soil or other loose material The rock material that breaks down to eventually form soil. Solid rock at surface is outcrop Most is buried beneath sediments Sedimentary rock composes most of lithosphere

Igneous Rock Rock formed when molten (melted) materials harden The original rock It all started here Extrusive - intrusive

Intrusive Igneous Extrusive Igneous 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 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

Extrusive Igneous Intrusive Igneous Breaks surface as lava and then cools and hardens Intrusive Igneous Magma cools and hardens below surface and then is exposed above surface by mountain building

Sedimentary Rock Consolidation 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 Rocks 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. Compaction Cementation

By compacting sediments By crystallization from dissolved minerals

Sedimentary Strata

Metamorphic Rocks Originally igneous/sedimentary Changed 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

Foliation Layering formed as a consequence of the alignment of mineral grains, or of compositional banding in a metamorphic rock.

The Rock Cycle

Distribution of Rock Classes

Geologic Time Figure 13-18

Geomorphic Processes