Dynamic Earth

Plate Tectonics, Earthquakes, Subduction, and other

significant events

Earth is a System

Integrated system consisting of rock, air, water, and living things that all interact with one another--Biosphere

• Geosphere—solid part• Atmosphere—mixture of gases to make air

we breath• Hydosphere—all water on or near Earth’s

surface• Lithosphere---land we live on

Discovering Earth’s Interior

What is the Lithosphere?

• The crust and part of the upper mantle = lithosphere–100 km thick

–Less dense than the material below it so it “floats”

What is the Asthenoshere?

• The plastic layer below the lithosphere = asthenosphere

• The plates of the lithosphere float on the asthenosphere

Plate Tectonics

Theory of Continental Drift

• http://www.youtube.com/watch?v=_5q8hzF9VVE

Global Tectonic Movement

Causes of Plate Tectonics

Convection Currents

• Hot magma in the Earth moves toward the surface, cools, then sinks again.

• Creates convection currents beneath the plates that cause the plates to move.

Unlike volcanoes that emerge from collision zones between tectonic plates, hotspot volcanoes form in the middle of the plates. The prevalent theory for how a mid-plate volcano forms is that a single upwelling of hot, buoyant rock rises vertically as a plume from deep within Earth’s

mantle – the layer found between the planet’s crust and core – and supplies the heat to feed volcanic eruptions.

A map view of seismic shear-wave speed in Earth’s upper mantle. The warm colors highlight slow wave-speed channels. Where present, the

channels align with the direction of tectonic-plate motion, shown as dashed lines.

Features of Divergent Boundaries

• Mid-ocean ridges

• rift valleys

• fissure volcanoes

Mid-Atlantic RidgeMid-Atlantic Ridge

Go to Inside Planet Earth DVD—special features—mid atlantic ridge.

Bill Nye: sea floor spreading http://www.youtube.com/watch?v=GyMLlLxbfa4

Sea Floor Spreading

Hypothermal Vents

Pillow Lava forms when magma cools in water. This is evidence of volcanic activity!

This shows you the age of the sea floor. The red areas This shows you the age of the sea floor. The red areas are new rocks and the blue areas are the oldest oceanic are new rocks and the blue areas are the oldest oceanic rock.rock.

Iceland is spreading Iceland is spreading open on the Mid-open on the Mid-Atlantic Ridge!Atlantic Ridge!

Can you see where the Mid-Atlantic Ridge bisects Iceland? This is a rift valley!

Subduction is a process where the ocean floor sinks back into the mantle at a deep ocean

trench.

Convergent Boundaries

• Boundaries between two plates that are colliding

• There are 3 types…

Type 1• Ocean plate colliding with a less

dense continental plate• Subduction Zone: where the less

dense plate slides under the more dense plate

• VOLCANOES occur at subduction zones

Aleutian Islands, Alaska

Type 2

• Ocean plate colliding with another ocean plate

• The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH

Type 3

• A continental plate colliding with another continental plate

• Have Collision Zones:–a place where folded and thrust

faulted mountains form.

Transform Fault Boundaries

• Boundary between two plates that are sliding past each other

• EARTHQUAKES along faults

Earthquake Belts

Earthquakes

• An earthquake is the shaking and trembling that results from the sudden movement of part of the Earth’s crust.

• The most common cause of earthquakes is faulting. During faulting, energy is released. Rocks continue to move until the energy is used up.

Tsunamis

• Earthquakes which occur on the ocean floor produce giant sea waves called tsunamis. Tsunamis can travel at speeds of 700 to 800 km per hour. As they approach the coast, they can reach heights of greater than 20 meters.

Focus

• Most faults occur between the surface and a depth of 70 kilometers.

• The point beneath the surface where the rocks break and move is called the focus. The focus is the underground origin of an earthquake.

Epicenter

• Directly above the focus, on the Earth’s surface is the epicenter. Earthquake waves reach the epicenter first. During an earthquake, the most violent shaking is found at the epicenter.

Ring of Fire

Pacific Ring

Seismic Risk Map of the U.S.

• http://earthquake.usgs.gov/learning/animations/

Formation of a Volcano

Volcanic Eruptions

• During volcanic eruptions, many rock fragments are blown into the air. The smallest particles are called volcanic dust. (less than 0.25 mm)

• Volcanic Ash ( 0.25 -5mm) falls to the Earth and forms small rocks.

• Volcanic bombs (a few cm to several meters) are molten and harden as they travel through the air.

Cinder Cone Volcano

Capulan Volcano National Monument

Shield Volcanoes

Mount Vesuvius-composite volcano

Composite Volcano

Effects of Volcanic Eruptions

• Volcanic Ash mixing with watter produces mudflows

• Volcanic Ash buries crops

• Volcanic Ash enters the troposphere and sometimes the stratosphere impacting amount of sunlight and temperatures on Earth

Get textbooks

• Complete questions #1-5 on page 94.

• Include the question in your answer.

Erosion

• Water erosion by rivers and oceans dramatically changes the Earth’s surface

• Wind erosion blows away top soil and erodes soft rocks, such as sandstone.

Dust bowl video clip

Go to discovery education

• Atomosphere video clip 4:40 min

Atmospheric Layers

Structure of the Atmosphere

Thermosphere

Mesosphere

Ozone MaximumStratosphere

Troposphere

Temperature

• Nitrogen 78%• Oxygen 20%• Argon 0.9%• CO2 0.04%• Water Vapor 1%

Thermosphere

• Absorbs harmful solar radiation resulting in the Aurora Borealis or Northern Lights

Atmospheric Circulations

Source: Wikipedia

Energy received at the surface depends on:1) Sun angle with respect to surface.2) Path of solar radiation through the atmosphere.

Source: Wikipedia

Solar Radiation Entering the Atmosphere

• Absorbed by gases and clouds – goes to heating (19%)• Scattered and Reflected by Gas Molecules, Clouds, Aerosols, and the Earth’s surface (30%)

About 51%Source: Ahrens, C. D., 2008: Essentials of Meteorology, An Invitation to the Atmosphere (5th Edition)

Earth’s Energy BalanceEarth’s overall average equilibrium temperature changes only slightly from year to year.

A balance exists between incoming solar energy (shortwave radiation) and outgoing energy from Earth to space (longwave radiation).

Source: Ahrens, C. D., 2008: Essentials of Meteorology, An Invitation to the Atmosphere (5th Edition)

Without greenhouse gases, the average surface temperature of the Earth would be –18° C

No greenhouse gases(only permanent gases)

The current atmosphere(with greenhouse gases)

33° C difference

Source: Ahrens, C. D., 2008: Essentials of Meteorology, An Invitation to the Atmosphere (5th Edition)

z

342

324

390

16540

235

30

0

7824

67

107

30

77

168

Surface Energy Balance: 168 = 390 – 324 + 24 + 78

Top of Atmosphere Energy Balance: 342 – 107 = 235

Sensible Heat

Latent Heat

Evapo-transpiration

Conduction

Long-wave Radiationfrom Clouds

Long-wave Radiationfrom Atmosphere

Long-wave RadiationAtmospheric Window

Longwave RadiationAbsorbed by Atmosphere

Longwave RadiationEmmited by Surface

Long-wave RadiationEmitted byAtmosphere

350

Outgoing Long-wave Radiation

Thermal heating

IncomingSolar Radiation

Shortwave

ReflectedShortwave radiation

by Clouds Aerosols

and Gases

ReflectedShortwave radiation

by Surface

AbsorbedShortwave radiation

by Surface

AbsorbedShortwave radiation

by Atmosphere

ReflectedShortwave radiation

Global Average Energy Balance

Atmosphere Energy Balance:67 + 350 + 24 + 78 = 324 + 165 + 30

Greenhouse Effect Animation

http://earthguide.ucsd.edu/earthguide/diagrams/greenhouse/

Terrestrial Ecosystems are an…• Integral part of global carbon system• Plants take in and store carbon dioxide from the atmosphere through photosynthesis• Below ground microbes decompose organic matter and release organic carbon back into the atmosphere

Cycle shows how nature’s sources of CO2 are self regulating – that which is released will be used again – Anthropogenic carbon not part of natures cycle – is in excess

www.bom.gov.au/.../ change/gallery/9.shtml

The World’s Water

• 97% Salt Water• 2.5 % Frozen Fresh

Water• .5% Usable Fresh

Water

Hydrosphere

• All water on or near the Earth’s surface

• Includes water in oceans, lakes, rivers, wetlands, polar ice caps, soil, rock layers beneath Earth’s surface and clouds.

http://www.youtube.com/watch?v=AF2BnTSTEFc

The Water Cycle

Water Cycle

Ocean circulation

Source: NOAA

View http://www.youtube.com/watch?

v=3niR_-Kv4SM

Source: WikipediaThermohaline currents 3:30min discovery education

Thermohaline convection quick lab

Layers of the Ocean

Global Ocean Temperatures

Storm Watch, Sept 1, 2011

North Atlantic Coast Sept 1, 2011

Hurricane Sandy Oct. 28, 2012

• High tide, full moon, high front pushing in from the mid-west—over 700 miles wide

Freshwater

• Freshwater is defined as having a low salt concentration — usually less than 1%.

• Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean).

Streams and riversThese are bodies of flowing water moving in one direction.

Wetlands are among the most productive ecosystems in the world, comparable to

rain forests and coral reefs.

Watersheds help the ecosystem

AquifersAquifers-

permeable materials that carry groundwater

Artesian FormationsArtesian

Formation- aquifer under nonporous layers holds groundwater

Artesian Wells- release water from Artesian formations

Recharge Zone

Biosphere

Closed System

• Energy enters the system but matter does not

• Earth is still a closed system with respect to matter but is still an open system with respect to energy

Open System

• Both matter and energy are exchanged between the system and the surrounding environment.