Warm Up 10/21(22) 1. When an earthquake occurs, energy radiates in all directions from its source, which is called the ____. a. faultc. seismic center.

Warm Up 10/21(22)Warm Up 10/21(22)1.1. When an earthquake occurs, energy radiates in all When an earthquake occurs, energy radiates in all

directions from its source, which is called the ____.directions from its source, which is called the ____.a. faulta. fault c. seismic centerc. seismic centerb. epicenterb. epicenter d. focusd. focus

2.2. The hypothesis that explains the release of energy during The hypothesis that explains the release of energy during an earthquake is called the ____.an earthquake is called the ____.a. moment magnitude hypothesisa. moment magnitude hypothesis c. Richter c. Richter hypothesishypothesisb. elastic rebound hypothesisb. elastic rebound hypothesis d. vibration d. vibration hypothesishypothesis

3.3. Most earthquakes are produced by the rapid release of Most earthquakes are produced by the rapid release of which kind of energy stored in rock subjected to great which kind of energy stored in rock subjected to great forces?forces?a. thermala. thermal c. chemicalc. chemicalb. elasticb. elastic d. Mechanicald. Mechanical

1. d, 2. b, 3. b

Earth’s Layered Earth’s Layered StructureStructure

Chapter 8, Section 4Chapter 8, Section 4

Layers Defined by CompositionLayers Defined by Composition If Earth were made up of the same If Earth were made up of the same

materials throughout its interior, seismic materials throughout its interior, seismic waves would travel in straight lines at waves would travel in straight lines at constant speedsconstant speeds

Seismic waves reaching seismographs Seismic waves reaching seismographs located farther from an earthquake travel located farther from an earthquake travel at faster average speeds, due to increased at faster average speeds, due to increased pressure at depthpressure at depth

Earth’s interior consists of three major Earth’s interior consists of three major zones defined by its chemical composition zones defined by its chemical composition – the crust, mantle, and core– the crust, mantle, and core

Paths of Seismic RaysPaths of Seismic Rays

The CrustThe Crust Crust –Crust – thin, rocky, outer layer of Earth; thin, rocky, outer layer of Earth;

divided into oceanic and continental crustdivided into oceanic and continental crust The oceanic crust is roughly 7 kilometers The oceanic crust is roughly 7 kilometers

thick and composed of the igneous rocks thick and composed of the igneous rocks basalt and gabbrobasalt and gabbro

The continental crust is 8-75 kilometers The continental crust is 8-75 kilometers thick (avg. 40 km) and consists mostly of thick (avg. 40 km) and consists mostly of the granitic rock granodioritethe granitic rock granodiorite

The rocks of the oceanic crust are younger The rocks of the oceanic crust are younger then the rocks of the continental crustthen the rocks of the continental crust

Mantle and CoreMantle and Core

Mantle – Mantle – a solid, rocky shell that a solid, rocky shell that extends to a depth of 2890 kmextends to a depth of 2890 km

Over 82% of Earth’s mass is Over 82% of Earth’s mass is contained in the mantlecontained in the mantle

The boundary between the crust and The boundary between the crust and mantle represents a chemical mantle represents a chemical composition changecomposition change

Core – Core – a sphere composed of an a sphere composed of an iron-nickel alloyiron-nickel alloy

Concept CheckConcept Check

What is the composition of the core?What is the composition of the core? An iron-nickel alloyAn iron-nickel alloy

Layers Defined by Physical Layers Defined by Physical PropertiesProperties

Earth’s interior has a gradual increase in Earth’s interior has a gradual increase in temperature, pressure, and density with temperature, pressure, and density with depthdepth

Depending on the physical environment Depending on the physical environment (temperature and pressure), a material (temperature and pressure), a material may behave like a brittle solid, a putty, or may behave like a brittle solid, a putty, or a liquida liquid

Earth can be divided into layers based on Earth can be divided into layers based on physical properties – the lithosphere, physical properties – the lithosphere, asthenosphere, outer core, and inner core.asthenosphere, outer core, and inner core.

Lithosphere and AsthenosphereLithosphere and Asthenosphere

Lithosphere – Lithosphere – relatively cool, rigid relatively cool, rigid shell consisting of the crust and shell consisting of the crust and upper most mantleupper most mantle

Averages about 100 kilometers in Averages about 100 kilometers in thicknessthickness

Asthenosphere – Asthenosphere – soft, soft, comparatively weak layer beneath comparatively weak layer beneath the lithospherethe lithosphere

The rocks within the asthenosphere The rocks within the asthenosphere are close enough to their melting are close enough to their melting points that they are easily deformedpoints that they are easily deformed

Lower MantleLower Mantle

From a depth of 660 km down to From a depth of 660 km down to near the base of the mantlenear the base of the mantle

More rigid layer that is still prone to More rigid layer that is still prone to gradual flowgradual flow

At the bottom of the mantle, rocks At the bottom of the mantle, rocks behave more like those in the behave more like those in the asthenosphereasthenosphere

Inner and Outer CoreInner and Outer Core

The core, which is composed of an The core, which is composed of an iron-nickel alloy, is divided into two iron-nickel alloy, is divided into two regions with different physical regions with different physical propertiesproperties

Outer Core –Outer Core – liquid layer 2260 km liquid layer 2260 km thick, flow produces Earth’s magnetic thick, flow produces Earth’s magnetic fieldfield

Inner Core –Inner Core – sphere with a radius of sphere with a radius of 1220 km, compressed into a solid 1220 km, compressed into a solid state by immense pressurestate by immense pressure

Earth’s Layered StructureEarth’s Layered Structure

Concept CheckConcept Check

Why is the inner core solid?Why is the inner core solid? It is under extreme pressure and is It is under extreme pressure and is

compressed into a solid as a resultcompressed into a solid as a result

Discovering Earth’s LayersDiscovering Earth’s Layers Moho –Moho – boundary separating the crust from the boundary separating the crust from the

mantle where the velocity of seismic waves mantle where the velocity of seismic waves abruptly increasesabruptly increases

Seismic waves from even small earthquakes Seismic waves from even small earthquakes can travel around the worldcan travel around the world

The outer core causes P waves that travel The outer core causes P waves that travel through it to arrive several minutes after through it to arrive several minutes after expected and are bent by 100expected and are bent by 100oo away from the away from the earthquake (shadow zone)earthquake (shadow zone)

It was further shown that S waves do not travel It was further shown that S waves do not travel through the outer core, making geologists through the outer core, making geologists conclude that the outer core is composed of a conclude that the outer core is composed of a liquidliquid

Concept CheckConcept Check

What is the Moho?What is the Moho? The boundary between the crust and The boundary between the crust and

the mantlethe mantle

Discovering Earth’s CompositionDiscovering Earth’s Composition Early seismic data and drilling technology Early seismic data and drilling technology

indicate that the continental crust is indicate that the continental crust is mostly made of lighter, granitic rocksmostly made of lighter, granitic rocks

The crust of the ocean floor has a baslatic The crust of the ocean floor has a baslatic compositioncomposition

The composition of the mantle and core is The composition of the mantle and core is known from more indirect dataknown from more indirect data

Scientists use lava and meteorites to infer Scientists use lava and meteorites to infer the composition of the mantle and corethe composition of the mantle and core

Earth’s core is thought to be mainly dense Earth’s core is thought to be mainly dense iron and nickel, similar to metallic iron and nickel, similar to metallic meteorites. The surrounding mantle is meteorites. The surrounding mantle is believed to be composed of rocks similar believed to be composed of rocks similar to stony meteoritesto stony meteorites

Earth’s Interior Showing P and S Earth’s Interior Showing P and S Wave PathsWave Paths

AssignmentAssignment

Read Chapter 8, Section 4 (pg. 233-237)Read Chapter 8, Section 4 (pg. 233-237) Do 8.4 Assessment #1-6 (pg. 237)Do 8.4 Assessment #1-6 (pg. 237)