36
Lectures
30
minutes/lecture
1.
Origin of the Universe
In the beginning, there was no need for geology because there were no rocks, minerals, or Earth. This lecture takes a "big picture" look at the formation and early evolution of the universe.
1.
Origin of the Universe
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19.
Streams—The Major Agent of Erosion
Despite holding only a tiny fraction of the world's fresh water, streams are the major agent of erosion wherever water can exist, including the desert. Streams are either interior (terminating inland) or exterior (ending in the ocean).
19.
Streams—The Major Agent of Erosion
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2.
Origin of the Solar System
The planets formed from a disc of cosmic dust rotating around the Sun. The composition of the planets varies. Those nearest the Sun are made of rock, while those most distant are made of gases.
2.
Origin of the Solar System
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20.
Sculpting of the Landscape
Surprisingly, there is no scientific consensus on the process of landscape evolution. One prominent theory, proposed by William Davis, sees land evolving through three stages of maturity due to stream erosion.
20.
Sculpting of the Landscape
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3.
Continental Drift
Until the 20th century, geologists believed that the size, shape, and location of the continents had been fixed in their present configuration for billions of years. Then the theory of plate tectonics changed everything.
3.
Continental Drift
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21.
Stream Erosion in Arid Regions
With minor modifications, Davis's theory on the three stages of a stream's life holds true for arid regions as well as humid regions. Nevada is typical of the process of stream erosion in arid regions.
21.
Stream Erosion in Arid Regions
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4.
Plate Tectonics
This lecture describes plate tectonics—the rifting of continents and spreading of the sea floor; the force that drives this process; and the cyclic creation, breaking up, and reformation of supercontinents.
4.
Plate Tectonics
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22.
Ice Sculpts the Final Scene
Glaciers are second only to streams as an agent of erosion. In areas such as the Alps and Canadian Rockies, the combined effects of stream and glacial erosion have carved some of the most spectacular scenery on the planet.
22.
Ice Sculpts the Final Scene
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5.
The Formation of Minerals
A full understanding of Earth's origin, the evolution of its surface, and how processes shape the land requires knowledge of minerals, how they form, and their basic classification.
5.
The Formation of Minerals
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23.
Groundwater
Earth's largest readily available source of fresh water is groundwater. This lecture looks at the types of rock most suitable for storing groundwater. Those that produce water most easily are classified as aquifers.
23.
Groundwater
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6.
Classification of Minerals
Minerals are classified by their dominant, negatively charged grouping (anion). By far, the major rock-forming minerals are silicates built around the silicate anion. All other minerals are classified as non-silicates.
6.
Classification of Minerals
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24.
The Production of Groundwater
Overproduction of an aquifer usually results in the lowering of the water table. Groundwater is not a renewable resource. It may take hundreds of thousands of years to replace a gallon of groundwater with a new gallon.
24.
The Production of Groundwater
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7.
The Identification of Minerals
For the average geologist in the field, mineral identification is made based on a series of physical properties. Color streak, cleavage, acid reaction, and hardness are four such tests.
7.
The Identification of Minerals
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25.
Karst Topography
One of the most spectacular results of groundwater in action is karst topography—irregular topography created by the surface and groundwater dissolution of underlying soluble rock, usually limestone.
25.
Karst Topography
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8.
Kinds of Rocks
Of the three types of rock—igneous, sedimentary, and metamorphic—igneous rocks constitute 80 percent of Earth's crust. They are classified and named based on their texture and mineral composition.
8.
Kinds of Rocks
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26.
Groundwater Contamination
Nearly every human activity, from fertilizing yards to parking cars, has the potential to contaminate groundwater. Poorly designed and built landfills rank high among potential contaminants.
26.
Groundwater Contamination
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9.
Sedimentary Rocks
Sedimentary rocks form from the products of weathering and cover 75 percent of Earth's land surface. As a result, they are the type of rock that is normally seen exposed at Earth's surface.
9.
Sedimentary Rocks
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27.
Rock Deformation
Deformation is any process in which rock changes in size and/or shape. The three types of deformation are elastic, plastic, and brittle, corresponding to rocks that "bounce back," bend, and break.
27.
Rock Deformation
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10.
Metamorphic Rocks
A metamorphic rock is any rock that forms from a previously existing rock as the result of heat, pressure, and chemically active fluids. This process takes place only at great depth.
10.
Metamorphic Rocks
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28.
The Geologic Structures
Rock structures form as a result of the application of stress beyond the strength of the rock. The three basic rock structures are folds, faults, and joints. This lecture focuses on folds, which are caused by compression.
28.
The Geologic Structures
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11.
Volcanic Activity
This lecture introduces volcanism, which is associated with three types of sites: convergent plate margins, divergent plate margins, and hot spots. The composition of magma is crucial in determining the intensity of an eruption.
11.
Volcanic Activity
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29.
Faults and Joints
Faults and joints comprise the two types of brittle deformation. Rocks move along faults. There is little or no movement along joints. One well-known fault is the San Andreas, a strike-slip fault.
29.
Faults and Joints
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12.
Phases of Volcanic Activity
The site of an eruption and the type of magma involved govern whether the resulting volcano will be a cinder cone, a shield volcano, or a strato- or composite volcano. Eruptions are further classified based on severity.
12.
Phases of Volcanic Activity
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30.
Earthquakes
Earthquakes occur in the same regions as the most violent volcanoes. Both result from the activity of convergent plate or divergent plate margins. Convergent plate margins produce the most violent of both events.
30.
Earthquakes
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13.
The Hawaiian Islands and Yellowstone Park
The Hawaiian Islands resulted from the movement of the Pacific plate over a volcanic hot spot. Yellowstone Park also sits over a hot spot that caused violent eruptions in prehistory. Another such eruption is likely.
13.
The Hawaiian Islands and Yellowstone Park
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31.
Damage from Earthquakes
The intensity of an earthquake refers to the observed results of the quaking and the amount of damage. An earthquake's magnitude measures the amount of Earth movement. Tsunamis are an earthquake-generated phenomenon.
31.
Damage from Earthquakes
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14.
Mass Wasting—Gravity at Work
Although mass wasting is one of the most important processes responsible for the evolution of the landscape, most people are unaware of its existence. The driving force of mass wasting is gravity.
14.
Mass Wasting—Gravity at Work
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32.
Seismology
Earthquakes have been detected for centuries with simple devices, but the ability to study the full impact of earthquakes awaited the invention of a seismograph that could not only detect but actually measure Earth movement.
32.
Seismology
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15.
Mass Wasting Processes
This lecture describes how mass wasting works and where to observe it. Although flows, slides, and falls account for the most dramatic forms of mass wasting, by far the greatest change is achieved by creep.
15.
Mass Wasting Processes
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33.
The Formation of Mountains
Mountains are of four types: volcanic, domal, block-fault, and foldbelt. The most impressive are foldbelt mountains such as the Himalayas, which are created by colliding plates at zones of subduction.
33.
The Formation of Mountains
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16.
Weathering
Weathering is any process whereby rocks either disintegrate or decompose. The primary agent of physical weathering is the freezing and thawing of water, known as frost wedging.
16.
Weathering
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34.
Orogenic Styles
Orogeny refers to the processes that create foldbelt mountains. These form under three scenarios: ocean-continent collisions, ocean-island arc-continent collisions, and continent-continent collisions.
34.
Orogenic Styles
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17.
Soils and the Clay Minerals
This lecture explores why soils are so critical to sustaining plant life. Clay minerals turn out to be the key component. Different climates have characteristic soil types, some of which are ideal for agriculture.
17.
Soils and the Clay Minerals
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35.
Economic Geology of Coal
Coal comes from wood that has been preserved in environments where oxygen and microbial activity is low. Coal is ranked by its carbon content, which varies widely in the abundant deposits in the United States.
35.
Economic Geology of Coal
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18.
Climate and the Type of Soils
Soil is the end product of a complex series of factors, the most important of which is climate. The type of soil that forms is controlled by the combination of annual precipitation and temperature.
18.
Climate and the Type of Soils
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36.
Economic Geology of Petroleum
Petroleum is formed when marine material is buried in porous rock capped by an impermeable layer. Predictions about the inevitable decrease and disappearance of oil resources appear to be all too accurate.
36.
Economic Geology of Petroleum
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48
Lectures
30
minutes/lecture
1.
Geology's Impact on History
If you could view Earth's history at high speed, you'd see continents whiz about, ocean basins grow and shrink, and mountain ranges rise and erode away. This lecture sets the stage for investigating our dynamic planet.
1.
Geology's Impact on History
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25.
Anatomy of an Earthquake—Sumatra
The 2004 Sumatra earthquake produced a massive tsunami that killed more than 200,000 people around the Indian Ocean. We look at the complex tectonic forces behind this cataclysm.
25.
Anatomy of an Earthquake—Sumatra
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2.
Geologic History—Dating the Earth
Discovering Earth's exact age took centuries of detective work. Rock strata provide relative ages, but only with the discovery of radioactivity was it possible to determine the absolute geologic timescale.
2.
Geologic History—Dating the Earth
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26.
History of Plate Motions—Where and Why
Earth's tectonic plates have been moving for at least as long as scientists can see back into the geologic record. Over time the continental fragments collect into supercontinents and then break apart again.
26.
History of Plate Motions—Where and Why
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3.
Earth's Structure—Journey to Earth's Center
Analysis of seismic waves from earthquakes allows scientists to map the structure inside Earth. Using this technique, we take a modern-day journey to the center of the Earth in the style of Jules Verne.
3.
Earth's Structure—Journey to Earth's Center
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27.
Assembling North America
North America has a fascinating geologic history, having continuously grown in size through collisions with other continents. The process of growth has been very different on the East and West coasts.
27.
Assembling North America
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4.
Earth's Heat—Conduction and Convection
We reverse the direction of the previous lecture to see how heat flows from the center of Earth toward the surface, exploring the phenomena of heat radiation, conduction, and convection.
4.
Earth's Heat—Conduction and Convection
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28.
The Sun-Driven Hydrologic Cycle
As fast as plate tectonics creates mountains, erosion tears them down. The principal agents of erosion are water and ice, which are part of a continuous cycle of moving water called the hydrologic cycle.
28.
The Sun-Driven Hydrologic Cycle
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5.
The Basics of Plate Tectonics
The theory of plate tectonics accounts for the existence of continents, oceans, mountains, earthquakes, volcanoes, mineral resource distribution, climate changes, and many other aspects of our planet.
5.
The Basics of Plate Tectonics
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29.
Water on Earth—The Blue Planet
Earth is unique in the solar system for having liquid water at its surface. Water is the single most important substance on our planet, controlling much of geology and allowing for the evolution of life.
29.
Water on Earth—The Blue Planet
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6.
Making Matter—The Big Bang and Big Bangs
We investigate the big bang and the early evolution of the universe to learn the origin of atoms, stars, and planets. The supernovae of dying stars played a key role in forging heavy elements.
6.
Making Matter—The Big Bang and Big Bangs
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30.
Earth's Atmosphere—Air and Weather
Earth's gravity is strong enough to hold onto an atmosphere of nitrogen and oxygen, while lighter gases have long since been lost to space. We explore the structure of the atmosphere and its circulation.
30.
Earth's Atmosphere—Air and Weather
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7.
Creating Earth—Recipe for a Planet
The solar system formed 4.6 billion years ago when a cloud of gas, dust, and ice began to collapse and rotate, with Earth accreting in the inner region of the disk. An enormous collision with the proto-Earth produced the Moon.
7.
Creating Earth—Recipe for a Planet
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31.
Erosion—Weathering and Land Removal
A mountain on the Moon can last for billions of years, but the same mountain on Earth is worn down in only tens of millions of years. The reason is the rapid rate of erosion on Earth due to its atmosphere and hydrosphere.
31.
Erosion—Weathering and Land Removal
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8.
The Rock Cycle—Matter in Motion
Though rocks may seem eternal, they are part of a continuous cycle of changing forms called the rock cycle, which begins with igneous rocks and can involve sedimentary and metamorphic phases.
8.
The Rock Cycle—Matter in Motion
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32.
Jungles and Deserts—Feast or Famine
The circulation of air within the atmosphere occurs predominantly in the form of six large convecting cycles called Hadley, Ferrel, and Polar cells. These control the distribution of precipitation and therefore of ecosystems.
32.
Jungles and Deserts—Feast or Famine
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9.
Minerals—The Building Blocks of Rocks
Rocks are made of minerals, which in turn are composed of different elements. Silicon and oxygen are the two most abundant elements in Earth's mantle and crust, and most rocks contain them.
9.
Minerals—The Building Blocks of Rocks
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33.
Mass Wasting—Rocks Fall Downhill
Once rock is broken into sediment, gravity makes sure that it heads downhill. Such "mass wasting" can occur as quickly as a landslide or as slowly as the piecemeal creep caused by repeated freezing and thawing.
33.
Mass Wasting—Rocks Fall Downhill
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10.
Magma—The Building Mush of Rocks
Most magma is generated beneath mid-ocean ridges, where plates move apart and rock moves toward the surface to fill the gaps. Magma forms in these places due to a process called pressure release.
10.
Magma—The Building Mush of Rocks
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34.
Streams—Shaping the Land
Once sediment is eroded and moved downhill, streams do most of the work from there. Streams are like a giant network of highways, continuously carrying rock from the mountains to the sea.
34.
Streams—Shaping the Land
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11.
Crystallization—The Rock Cycle Starts
When magma cools below certain temperatures, solid mineral crystals begin to grow. With continued cooling the entire magma will eventually crystallize, and the result is an igneous rock.
11.
Crystallization—The Rock Cycle Starts
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35.
Groundwater—The Invisible Reservoir
There is 100 times more water in the ground than in streams and lakes combined. Groundwater rarely consists of underground rivers, but rather of water percolating slowly though tiny pore spaces within rocks.
35.
Groundwater—The Invisible Reservoir
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12.
Volcanoes—Lava and Ash
Volcanoes form where magma reaches the surface and erupts—at which point the magma becomes lava. The different kinds of volcanoes are related to the tectonic settings in which they occur.
12.
Volcanoes—Lava and Ash
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36.
Shorelines—Factories of Sedimentary Rocks
The pounding of ocean waves is so strong that it sets all the continents reverberating. Shorelines are energetic environments where wave energy erodes rock and transports the sediments that become sedimentary rocks.
36.
Shorelines—Factories of Sedimentary Rocks
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13.
Folding—Bending Blocks, Flowing Rocks
Most rock of the crust and mantle is solid. And yet, over long timescales, the crust and mantle are in motion, bending and flowing. This lecture shows how rocks deform in an elastic, plastic, or brittle manner.
13.
Folding—Bending Blocks, Flowing Rocks
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37.
Glaciers—The Power of Ice
Glaciers are slowly moving rivers of flowing ice. They are remarkably efficient agents of erosion, tearing away mountains faster than any other geologic process.
37.
Glaciers—The Power of Ice
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14.
Earthquakes—Examining Earth's Faults
More than 200,000 earthquakes are recorded each year. We examine the types of faults along which they occur and the aftermath, which in some cases can leave the Earth ringing like a gong for months.
14.
Earthquakes—Examining Earth's Faults
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38.
Planetary Wobbles and the Last Ice Age
There is a cyclical pattern in the alternation of cold glacial periods and warmer interglacials, primarily due to variations in Earth's orbital characteristics. These are called Milankovitch cycles.
38.
Planetary Wobbles and the Last Ice Age
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15.
Plate Tectonics—Why Continents Move
Continents move because they are the surface expression of mantle convection. Two main forces are directly responsible for plate motions: slab pull and ridge push.
15.
Plate Tectonics—Why Continents Move
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39.
Long-Term Climate Change
Long timescale variations in climate are controlled predominantly by plate tectonics. The global cooling that has occurred over the past 50 million years is largely due to the formation of the Himalayan Mountains.
39.
Long-Term Climate Change
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16.
The Ocean Seafloor—Unseen Lands
The seafloor shows a tremendous diversity of features that are related to plate tectonics and the process of mantle convection.
16.
The Ocean Seafloor—Unseen Lands
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40.
Short-Term Climate Change
This lecture looks at climate change on timescales of decades to thousands of years. Several factors affect climate at these shorter timescales, among them variations in sunlight, ocean current fluctuations, and volcanoes.
40.
Short-Term Climate Change
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17.
Rifts and Ridges—The Creation of Plates
Oceans undergo reincarnation: they repeatedly die and are reborn. The Atlantic Ocean is only 180 million years old and will eventually close up again. The Red Sea appears to be a new ocean in the making.
17.
Rifts and Ridges—The Creation of Plates
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41.
Climate Change and Human History
The course of human civilization, which began at the same time as the warm, stable climates of the current interglacial period, is strongly tied to small changes in global and regional climates.
41.
Climate Change and Human History
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18.
Transform Faults—Tears of a Crust
The San Andreas is a transform fault that separates the North American and Pacific plates. Transform faults are actually rare on land, but mid-ocean ridges are intersected by countless such features.
18.
Transform Faults—Tears of a Crust
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42.
Plate Tectonics and Natural Resources
Did you ever wonder why there is gold in California, coal in Indiana, and oil in Iraq? During the natural process of plate tectonics, valuable metals and ores become concentrated to levels much higher than they normally exist.
42.
Plate Tectonics and Natural Resources
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19.
Subduction Zones—Recycling Oceans
Subduction zones are the most geologically exciting places on Earth. Here the most destructive earthquakes and volcanoes occur, and forces are generated that may rip supercontinents apart.
19.
Subduction Zones—Recycling Oceans
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43.
Nonrenewable Energy Sources
Most of the energy that humans now consume is in the form of nonrenewable sources, notably oil, natural gas, and coal. Uranium for powering nuclear reactors is also a limited, nonrenewable source.
43.
Nonrenewable Energy Sources
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20.
Continents Collide and Mountains Are Made
When plate motions bring continents in contact with each other, the result is the formation of mountains. A notable example is the Himalayas, produced by the continental collision of India with China.
20.
Continents Collide and Mountains Are Made
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44.
Renewable Energy Sources
We will eventually get almost all of our energy from solar-driven sources. These include solar panels and passive solar heating. Wind power, hydroelectric power, and biomass are also ultimately derived from sunlight.
44.
Renewable Energy Sources
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21.
Intraplate Volcanoes—Finding the Hot Spots
For years intraplate volcanoes such as those that produced the Hawaiian Islands were lumped together under the catch-all name of "hot spots," but recent work is showing that Earth has many different ways of making a volcano.
21.
Intraplate Volcanoes—Finding the Hot Spots
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45.
Humans—Dominating Geologic Change
Life has been altering the planet over roughly the past 4 billion years. What is remarkable, however, is the rapidity with which humans have become Earth's most powerful agent of geologic change.
45.
Humans—Dominating Geologic Change
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22.
Destruction from Volcanoes and Earthquakes
The largest earthquakes and volcanic eruptions release as much energy as the simultaneous explosion of tens of thousands of nuclear weapons. We look at the human consequences of these events.
22.
Destruction from Volcanoes and Earthquakes
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46.
History of Life—Complexity and Diversity
Life on Earth began at least 3.85 billion years ago, almost as soon as the conditions of a stable ocean would allow it. The path of evolution since then has been a remarkable one, and an integral part of Earth's story.
46.
History of Life—Complexity and Diversity
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23.
Predicting Natural Disasters
Volcanoes can be easily monitored, and they reveal many clues to an impending eruption as the magma slowly forces its way toward the surface. Earthquakes, by contrast, are not yet predictable.
23.
Predicting Natural Disasters
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47.
The Solar System—Earth's Neighborhood
Although Earth is unique in our solar system for having complex life, it is not unique in geologic processes such as volcanism, earthquakes, mantle convection, erosion, and even stream and lake formation.
47.
The Solar System—Earth's Neighborhood
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24.
Anatomy of a Volcano—Mount St. Helens
We examine the eruption of Mount St. Helens on May 18, 1980, triggered when an earthquake caused a gigantic avalanche that released pent-up magma and gases, leveling trees for over 600 square kilometers.
24.
Anatomy of a Volcano—Mount St. Helens
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48.
The Lonely Planet—Fermi's Paradox
What are the chances that there are other civilizations in our galaxy? Given the delicate balance of conditions that have allowed life to flourish on Earth, that number may be astonishingly small.
48.
The Lonely Planet—Fermi's Paradox
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