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Warm Up 12/4 When does liquefaction occur? When does liquefaction occur? When loosely consolidated soils saturated with water are shaken by earthquake.

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Presentation on theme: "Warm Up 12/4 When does liquefaction occur? When does liquefaction occur? When loosely consolidated soils saturated with water are shaken by earthquake."— Presentation transcript:

1 Warm Up 12/4 When does liquefaction occur? When does liquefaction occur? When loosely consolidated soils saturated with water are shaken by earthquake waves When loosely consolidated soils saturated with water are shaken by earthquake waves What factors determine how much damage is inflicted on a building? What factors determine how much damage is inflicted on a building? Intensity and duration of vibrations, nature of material on which the structure is built, and design of the structure Intensity and duration of vibrations, nature of material on which the structure is built, and design of the structure Why is it incorrect to refer to tsunamis as tidal waves? Why is it incorrect to refer to tsunamis as tidal waves? Tidal waves are caused by the gravitational pull of the sun and moon, while tsunamis are caused by earthquakes Tidal waves are caused by the gravitational pull of the sun and moon, while tsunamis are caused by earthquakes

2 Go Bruins!

3 Earth’s Layered Structure

4 Layers Defined by Composition If Earth were made up of the same materials throughout its interior, seismic waves would travel in straight lines at constant speeds If Earth were made up of the same materials throughout its interior, seismic waves would travel in straight lines at constant speeds Seismic waves reaching seismographs located farther from an earthquake travel at faster average speeds, due to increased pressure at depth Seismic waves reaching seismographs located farther from an earthquake travel at faster average speeds, due to increased pressure at depth Earth’s interior consists of three major zones defined by its chemical composition – the crust, mantle, and core Earth’s interior consists of three major zones defined by its chemical composition – the crust, mantle, and core

5 Paths of Seismic Rays

6 The Crust Crust – thin, rocky, outer layer of Earth; divided into oceanic and continental crust Crust – thin, rocky, outer layer of Earth; divided into oceanic and continental crust The oceanic crust is roughly 7 kilometers thick and composed of the igneous rocks basalt and gabbro The oceanic crust is roughly 7 kilometers thick and composed of the igneous rocks basalt and gabbro The continental crust is 8-75 kilometers thick (avg. 40 km) and consists mostly of the granitic rock granodiorite The continental crust is 8-75 kilometers thick (avg. 40 km) and consists mostly of the granitic rock granodiorite The rocks of the oceanic crust are younger then the rocks of the continental crust The rocks of the oceanic crust are younger then the rocks of the continental crust

7 Mantle and Core Mantle – a solid, rocky shell that extends to a depth of 2890 km Mantle – a solid, rocky shell that extends to a depth of 2890 km Over 82% of Earth’s mass is contained in the mantle Over 82% of Earth’s mass is contained in the mantle The boundary between the crust and mantle represents a chemical composition change The boundary between the crust and mantle represents a chemical composition change Core – a sphere composed of an iron-nickel alloy Core – a sphere composed of an iron-nickel alloy

8 Layers Defined by Physical Properties Earth’s interior has a gradual increase in temperature, pressure, and density with depth Earth’s interior has a gradual increase in temperature, pressure, and density with depth Depending on the physical environment (temperature and pressure), a material may behave like a brittle solid, a putty, or a liquid Depending on the physical environment (temperature and pressure), a material may behave like a brittle solid, a putty, or a liquid Earth can be divided into layers based on physical properties – the lithosphere, asthenosphere, outer core, and inner core. Earth can be divided into layers based on physical properties – the lithosphere, asthenosphere, outer core, and inner core.

9 Lithosphere and Asthenosphere Lithosphere – relatively cool, rigid shell consisting of the crust and upper most mantle Lithosphere – relatively cool, rigid shell consisting of the crust and upper most mantle Averages about 100 kilometers in thickness Averages about 100 kilometers in thickness Asthenosphere – soft, comparatively weak layer beneath the lithosphere Asthenosphere – soft, comparatively weak layer beneath the lithosphere The rocks within the asthenosphere are close enough to their melting points that they are easily deformed The rocks within the asthenosphere are close enough to their melting points that they are easily deformed

10 Lower Mantle From a depth of 660 km down to near the base of the mantle From a depth of 660 km down to near the base of the mantle More rigid layer that is still prone to gradual flow More rigid layer that is still prone to gradual flow At the bottom of the mantle, rocks behave more like those in the asthenosphere At the bottom of the mantle, rocks behave more like those in the asthenosphere

11 Inner and Outer Core The core, which is composed of an iron-nickel alloy, is divided into two regions with different physical properties The core, which is composed of an iron-nickel alloy, is divided into two regions with different physical properties Outer Core – liquid layer 2260 km thick, flow produces Earth’s magnetic field Outer Core – liquid layer 2260 km thick, flow produces Earth’s magnetic field Inner Core – sphere with a radius of 1220 km, compressed into a solid state by immense pressure Inner Core – sphere with a radius of 1220 km, compressed into a solid state by immense pressure

12 Earth’s Layered Structure

13 Discovering Earth’s Layers Moho – boundary separating the crust from the mantle where the velocity of seismic waves abruptly increases Moho – boundary separating the crust from the mantle where the velocity of seismic waves abruptly increases Seismic waves from even small earthquakes can travel around the world Seismic waves from even small earthquakes can travel around the world The outer core causes P waves that travel through it to arrive several minutes after expected and are bent by 100 o away from the earthquake (shadow zone) The outer core causes P waves that travel through it to arrive several minutes after expected and are bent by 100 o away from the earthquake (shadow zone) It was further shown that S waves do not travel through the outer core, making geologists conclude that the outer core is composed of a liquid It was further shown that S waves do not travel through the outer core, making geologists conclude that the outer core is composed of a liquid

14 Discovering Earth’s Composition Early seismic data and drilling technology indicate that the continental crust is mostly made of lighter, granitic rocks Early seismic data and drilling technology indicate that the continental crust is mostly made of lighter, granitic rocks The crust of the ocean floor has a baslatic composition The crust of the ocean floor has a baslatic composition The composition of the mantle and core is known from more indirect data The composition of the mantle and core is known from more indirect data Scientists use lava and meteorites to infer the composition of the mantle and core Scientists use lava and meteorites to infer the composition of the mantle and core Earth’s core is thought to be mainly dense iron and nickel, similar to metallic meteorites. The surrounding mantle is believed to be composed of rocks similar to stony meteorites Earth’s core is thought to be mainly dense iron and nickel, similar to metallic meteorites. The surrounding mantle is believed to be composed of rocks similar to stony meteorites

15 Earth’s Interior Showing P and S Wave Paths

16 Assignment 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)


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