Earth Systems Science Unit 2 ReviewEarth's Structure and Composition

Earth's structure and composition are fundamental to understanding our planet's dynamics. From the solid inner core to the rocky crust, each layer plays a crucial role in shaping Earth's behavior. This knowledge helps explain phenomena like plate tectonics, earthquakes, and volcanic activity. The rock cycle, driven by these internal processes, continuously transforms Earth's surface. By studying the planet's composition and ongoing geological processes, scientists can better predict natural disasters, locate valuable resources, and unravel Earth's long history.

2.1

Internal structure of the Earth

2.2

Composition of the Earth's layers

2.3

Rock cycle and major rock types

2.4

Earth's magnetic field and its significance

unit 2 review

Core Concepts

Earth is a dynamic planet consists of various layers and structures
Plate tectonics theory explains the movement and interaction of Earth's lithospheric plates
- Driven by convection currents in the mantle
- Causes earthquakes, volcanic eruptions, and mountain building (Himalayas)
The rock cycle describes the continuous transformation of rocks between igneous, sedimentary, and metamorphic forms
Earth's composition includes a solid inner core, liquid outer core, mantle, and crust
- Crust and uppermost mantle form the lithosphere
Geologic processes shape Earth's surface over time (weathering, erosion, deposition)
Understanding Earth's structure and composition helps predict natural disasters and locate resources (oil, minerals)

Earth's Layers

Crust: Outermost layer, varies in thickness (oceanic crust ~5-10 km, continental crust ~30-50 km)
- Oceanic crust is denser and thinner than continental crust
Mantle: Layer between crust and core, ~2,900 km thick
- Upper mantle is solid, lower mantle is partially molten
- Convection currents in the mantle drive plate tectonics
Outer Core: Liquid layer, ~2,300 km thick, composed primarily of iron and nickel
- Convection in the outer core generates Earth's magnetic field
Inner Core: Solid layer, ~1,200 km thick, composed primarily of iron and nickel
- Extremely high pressure causes the inner core to be solid despite high temperatures
Lithosphere: Rigid outer layer, includes crust and uppermost mantle
Asthenosphere: Partially molten layer beneath the lithosphere, allows lithospheric plates to move

Plate Tectonics

Theory that explains the large-scale motion of Earth's lithosphere
Lithosphere is divided into several plates that move relative to each other
Plate boundaries: Divergent, convergent, and transform
- Divergent boundaries: Plates move apart, creating new crust (mid-ocean ridges)
- Convergent boundaries: Plates collide, causing subduction, mountain building, and volcanism (Andes Mountains)
- Transform boundaries: Plates slide past each other, causing earthquakes (San Andreas Fault)
Driving forces: Convection currents in the mantle, slab pull, and ridge push
Evidence for plate tectonics: Seafloor spreading, magnetic anomalies, and fossil distributions
Plate tectonics explains the formation and distribution of landforms, earthquakes, and volcanic activity

Rock Cycle and Types

Rock cycle: Continuous process of rock formation and transformation
Igneous rocks: Formed from the cooling and solidification of magma or lava
- Intrusive (plutonic) rocks: Cool slowly beneath Earth's surface (granite)
- Extrusive (volcanic) rocks: Cool rapidly on Earth's surface (basalt)
Sedimentary rocks: Formed from the compaction and cementation of sediments
- Clastic sedimentary rocks: Composed of rock fragments (sandstone, conglomerate)
- Chemical sedimentary rocks: Formed by precipitation from solution (limestone, rock salt)
- Organic sedimentary rocks: Formed from the remains of organisms (coal, chert)
Metamorphic rocks: Formed from the transformation of existing rocks under heat and pressure
- Foliated metamorphic rocks: Have a layered appearance (gneiss, schist)
- Non-foliated metamorphic rocks: Do not have a layered appearance (marble, quartzite)

Earth's Composition

Crust: Primarily composed of silicate minerals (feldspars, quartz)
- Oceanic crust: Mafic composition (rich in magnesium and iron), denser than continental crust
- Continental crust: Felsic composition (rich in silica and aluminum), less dense than oceanic crust
Mantle: Primarily composed of silicate minerals (olivine, pyroxene)
- Upper mantle: Solid, composed of peridotite
- Lower mantle: Partially molten, composed of silicate minerals and iron
Core: Primarily composed of iron and nickel
- Outer core: Liquid, composed of iron and nickel
- Inner core: Solid, composed of iron and nickel
Elemental abundance: Oxygen (46.6%), silicon (27.7%), aluminum (8.1%), iron (5.0%), calcium (3.6%), and others
Mineral composition varies with depth due to changes in pressure and temperature

Geologic Processes

Weathering: Breakdown of rocks and minerals at Earth's surface
- Physical weathering: Mechanical disintegration of rocks (frost wedging, exfoliation)
- Chemical weathering: Alteration of rocks by chemical reactions (dissolution, oxidation)
Erosion: Removal and transportation of weathered material by water, wind, ice, or gravity
- Fluvial erosion: Erosion by running water (rivers, streams)
- Glacial erosion: Erosion by glaciers and ice sheets (U-shaped valleys, cirques)
- Aeolian erosion: Erosion by wind (desert landscapes, sand dunes)
Deposition: Settling of transported sediments
- Fluvial deposition: Deposition by running water (alluvial fans, deltas)
- Glacial deposition: Deposition by glaciers and ice sheets (moraines, drumlins)
- Aeolian deposition: Deposition by wind (loess, sand dunes)
Mass wasting: Downslope movement of rock and soil under the influence of gravity (landslides, rockfalls)

Key Terms and Definitions

Lithosphere: Rigid outer layer of Earth, including the crust and uppermost mantle
Asthenosphere: Partially molten layer beneath the lithosphere, allowing for plate movement
Plate boundaries: Zones where lithospheric plates interact (divergent, convergent, transform)
Subduction: Process by which one plate descends beneath another at a convergent boundary
Mid-ocean ridge: Underwater mountain range formed by divergent plate boundaries
Fault: Fracture in Earth's crust along which movement has occurred
Earthquake: Sudden release of energy in Earth's crust, causing seismic waves
Volcano: Opening in Earth's surface through which magma, ash, and gases are expelled
Magma: Molten rock beneath Earth's surface
Lava: Molten rock that has been expelled onto Earth's surface
Igneous rock: Rock formed from the cooling and solidification of magma or lava
Sedimentary rock: Rock formed from the compaction and cementation of sediments
Metamorphic rock: Rock formed from the transformation of existing rocks under heat and pressure

Real-World Applications

Plate tectonics helps predict the location and frequency of earthquakes and volcanic eruptions
- Seismic hazard maps guide building codes and emergency preparedness plans
Understanding rock types and formations aids in the exploration and extraction of natural resources (oil, natural gas, minerals)
- Sedimentary basins are often targeted for oil and gas exploration
Geologic processes shape landscapes and influence land use planning
- Floodplains, coastal areas, and hillslopes require special considerations for development
Knowledge of Earth's composition and structure informs the study of other terrestrial planets (Mars, Venus)
Geologic time scale provides a framework for understanding Earth's history and the evolution of life
- Fossils and rock strata help reconstruct past environments and climates
Geologic hazards (landslides, sinkholes) are assessed and mitigated based on an understanding of Earth's structure and processes
Geothermal energy utilizes heat from Earth's interior for power generation (Iceland)

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