24
Lectures
30
minutes/lecture
1.
Nature Abhors Extremes
From thunderstorms to typhoons to driving winds, the world's weather is often tumultuous, destructive, and surprising. And yet, all these phenomena represent Nature's attempt to mitigate extreme conditions. In this introduction, begin to explore some of these extremes as you examine the great complexity of the world weather system.
1.
Nature Abhors Extremes
|
13.
The Global Atmospheric Circulation
After mastering the four forces that affect wind, step back to view their patterns of flow across the Earth's hemispheres. Examine the two models of air circulation that help account for large-scale air-circulation patterns and variations in temperature from the poles to the equator.
13.
The Global Atmospheric Circulation
|
2.
Temperature, Pressure, and Density
Why do cold and warm fronts exist? Can you dig a well so deep you cannot pump water from it? Find the answer to these and other questions as you explore three key concepts of weather—temperature, pressure, and density—and the equation that sums up their relationship: the ideal gas law.
2.
Temperature, Pressure, and Density
|
14.
Fronts and Extratropical Cyclones
In this lecture, you encounter some of the most dramatic air-flow patterns found in nature, the swift, turning winds of the cyclone. Trace the lifecycle of the extratropical cyclone, which draws its power from the huge energy generated when different air masses meet.
14.
Fronts and Extratropical Cyclones
|
3.
Atmosphere—Composition and Origin
What is air made of? Is it always true that hot air rises and cold air sinks? Learn more about the air that surrounds us and cushions us from the outer reaches of space, and examine the various layers that make up the earth's atmosphere.
3.
Atmosphere—Composition and Origin
|
15.
Middle Troposphere—Troughs and Ridges
Shift your eyes to the sky and examine what happens in a higher level of the atmosphere called the middle troposphere. With this examination, you discover two new features in large weather systems—troughs and ridges that occur in areas of very low and very high pressure—and see how these features affect the weather.
15.
Middle Troposphere—Troughs and Ridges
|
4.
Radiation and the Greenhouse Effect
Energy radiates all around us, streaming in from sunbeams and emanating from every object on Earth. Investigate the various kinds of radiation represented on the electromagnetic spectrum, and see how these forms of energy—assisted by the greenhouse effect—make life possible on our planet.
4.
Radiation and the Greenhouse Effect
|
16.
Wind Shear—Horizontal and Vertical
Expand your understanding of how air moves by taking a three-dimensional view of atmospheric circulation. Discover what happens when winds change direction and what conditions cause these changes in wind shear.
16.
Wind Shear—Horizontal and Vertical
|
5.
Sphericity, Conduction, and Convection
If all the Earth receives energy from the sun, why are there such wide temperature differences across the planet? Why do we have seasons? Answer these questions while learning about how heat moves through the atmosphere via two basic processes: conduction and convection.
5.
Sphericity, Conduction, and Convection
|
17.
Mountain Influences on the Atmosphere
In this lecture, investigate how mountains can disturb the atmosphere into which they intrude from below. Also, learn how these disturbances can be felt far and wide.
17.
Mountain Influences on the Atmosphere
|
6.
Sea Breezes and Santa Anas
Gain an understanding of how wind works as you explore the way temperature and pressure drive sea breezes during the day and land breezes at night. Then apply these findings to a dramatic wind condition, the famous Santa Ana winds of California.
6.
Sea Breezes and Santa Anas
|
18.
Thunderstorms, Squall Lines, and Radar
That familiar crash of thunder and the torrential rains that often accompany it are common weather during the warm season. Learn how these noisy storms can form near cold fronts associated with extratropical cyclones and see how scientists use radar to study these storms.
18.
Thunderstorms, Squall Lines, and Radar
|
7.
An Introduction to Atmospheric Moisture
Add a new element to your understanding of the atmosphere—water—and learn some basic facts about air's capacity to hold water vapor, including the impact of temperature on atmospheric moisture and the implications for weather.
7.
An Introduction to Atmospheric Moisture
|
19.
Supercells, Tornadoes, and Dry Lines
Delve deeper into tumultuous weather as you learn about the formation of towering supercell storms. You also take a detailed look at how the conditions that produce these storms can lead to deadly tornadoes.
19.
Supercells, Tornadoes, and Dry Lines
|
8.
Bringing Air to Saturation
Why does dew form on some mornings? Why does it take longer to cook food at higher elevations? Discover the answer to these questions as you learn about saturation: the point where air holds the highest amount of water vapor that it can contain.
8.
Bringing Air to Saturation
|
20.
Ocean Influences on Weather and Climate
With their massive volume and constantly moving currents, oceans provide a vast reservoir of energy. Explore how the winds help generate movement in the ocean and, in turn, how the oceans affect weather all over the world, creating a huge feedback loop that helps create our climate.
20.
Ocean Influences on Weather and Climate
|
9.
Clouds, Stability, and Buoyancy, Part 1
One of the most familiar and beautiful features of weather is the cloud. In this lecture, examine different kinds of clouds, learn how clouds are born, why and how they take their distinctive shapes, and what kinds of conditions are likely to produce clouds.
9.
Clouds, Stability, and Buoyancy, Part 1
|
21.
Tropical Cyclones
Building on your understanding of how the ocean affects weather, turn your attention to the tropical cyclone, generally known as the hurricane or typhoon. Examine the typical structures of the tropical cyclone, and investigate the conditions needed to unleash these dangerous storms.
21.
Tropical Cyclones
|
10.
Clouds, Stability, and Buoyancy, Part 2
Continue your discussion of clouds as you take a closer look at the climates and precipitation relating to this weather phenomenon. Discover why some clouds produce rain while others do not and see why deserts are often found on the lee side of mountains.
10.
Clouds, Stability, and Buoyancy, Part 2
|
22.
Light and Lightning
Here, you bring together all you've learned in earlier lectures about the composition of air, the electromagnetic spectrum, the condensation of liquid, and the role of oceans in our climate, and use that information to explore two dazzling phenomena: light and lightning.
22.
Light and Lightning
|
11.
Whence and Whither the Wind, Part 1
Move from clouds to wind as you begin to explore how and why air is transported around the globe. Examine how conditions, including differences in air pressure and temperature as well as the rotation of the Earth, determine where winds arise and the direction in which they blow.
11.
Whence and Whither the Wind, Part 1
|
23.
Prediction and Predictability
Scientists have learned a lot about how weather works and have developed sophisticated tools to predict what may happen in our weather. You learn about the sophisticated numerical models these experts use, as well as the inevitable limitations of those models.
23.
Prediction and Predictability
|
12.
Whence and Whither the Wind, Part 2
In addition to pressure differences and the Earth's rotational movement, two other forces help to determine the winds' strength and direction: friction and centripetal force. Learn about these two forces and examine how they shape the winds the world over.
12.
Whence and Whither the Wind, Part 2
|
24.
The Imperfect Forecast
Despite all their knowledge and tools, scientists cannot make perfect predictions. Find out why, using the example of Hurricane Rita in 2005, and explore the deep complexity of weather and climate that makes the subject of meteorology one that continues to fascinate.
24.
The Imperfect Forecast
|
36
Lectures
30
minutes/lecture
1.
Diving In—The Ocean Adventure
Begin your study of the ocean from every angle, examining Earth's watery realm in light of geology, biology, chemistry, meteorology, and other fields. In this lecture, survey the extent of the ocean and the approaches that oceanographers take to understanding it.
1.
Diving In—The Ocean Adventure
|
19.
Soft-Bodied Life in the Dark, Open Depths
Investigate the soft-bodied organisms that live at great depths and have no skeletons or shells. Little known until recently, this group includes a variety of creatures whose amorphous bodies are often destroyed by nets and who only came to light through studies from submersibles.
19.
Soft-Bodied Life in the Dark, Open Depths
|
2.
Explorers, Navigators, Pioneering Scientists
The early explorers of the ocean were interested in charting its islands, dimensions, and resources—and in using it as a highway for trade. Relive the exploits of these mariners, who included Europeans, Chinese, and Polynesians. Only later did scientific exploration of the ocean begin.
2.
Explorers, Navigators, Pioneering Scientists
|
20.
Swimming—The Many Fish in the Sea
Contrasting with free-floating plankton, nekton are the ocean's swimmers. In this lecture, study the most numerous nekton—fish—focusing on their streamlining, gills, schooling, and other adaptations. Also, examine mollusks, including the octopus, squid, and nautilus.
20.
Swimming—The Many Fish in the Sea
|
3.
Ocean Basics and Ocean Basins
As recently as the 1950s, geologists envisioned the ocean basins as a submerged version of the continents. Explore the topography of the seabed, discovering that it is shaped by geological forces fundamentally different from those on land.
3.
Ocean Basics and Ocean Basins
|
21.
Marine Birds, Reptiles, and Mammals
Turn to the nekton among birds, reptiles, and mammals. These feature some of the most magnificent creatures on the planet, including albatrosses, Sooty Shearwaters, sea turtles, manatees, seals, sea lions, whales, and dolphins. Focus on the adaptations that allow them to thrive in marine environments.
21.
Marine Birds, Reptiles, and Mammals
|
4.
Mapping the Sea—Soundings to Satellites
The ocean floor was once as mysterious as the surface of another planet. Investigate the technologies involved in measuring bathymetry, the undersea counterpart of topography. Weighted ropes and cables for gauging the depth of the sea have given way to sophisticated sonar from ships and radar from satellites.
4.
Mapping the Sea—Soundings to Satellites
|
22.
Whaling, Fisheries, and Farming the Ocean
Examine the economic exploitation of marine life, beginning with the history of whaling and continuing to the present, when fishing is the only significant source of hunted food. Weigh the alternatives of commercial fishing and mariculture in an era of rapidly declining fish populations.
22.
Whaling, Fisheries, and Farming the Ocean
|
5.
Habitats—Sunlit Shelves to the Dark Abyss
Take a tour of organisms that live from the shallows to the ocean floor. Learn how to classify ocean zones, and discover the importance of temperature, chemistry, nutrients, light, and other factors for different life forms—from active swimmers to passive floaters and bottom dwellers.
5.
Habitats—Sunlit Shelves to the Dark Abyss
|
23.
Where Sea Meets the Land and Why Coasts Vary
Have you ever walked along a beach or stood on a high cliff overlooking the sea and wondered how the land got to be that way? Learn how erosion, deposition, sea-level change, plate tectonics, and other factors have produced the characteristic coastlines of the world.
23.
Where Sea Meets the Land and Why Coasts Vary
|
6.
The Spreading Sea Floor and Mid-Ocean Ridges
What made the ocean floor the way it is? Trace the evidence that ocean basins are geologically young and that new oceanic crust is being continually formed at mid-ocean ridges, pushing and rifting continental plates in a process called plate tectonics.
6.
The Spreading Sea Floor and Mid-Ocean Ridges
|
24.
Where Rivers Meet the Sea—Estuaries and Deltas
River mouths, deltas, tidal inlets, fjords, and enclosed bays are places where freshwater and seawater mix. Explore these complex zones, which are among the most biologically productive ecosystems on Earth. Many marine organisms carry out key parts of their lifecycles in such environments.
24.
Where Rivers Meet the Sea—Estuaries and Deltas
|
7.
The Plunging Sea Floor and Deep-Sea Trenches
Investigate subduction zones, where oceanic crust plunges beneath an overriding tectonic plate. These margins are associated with deep-sea trenches, earthquakes, tsunamis, and volcanoes. Examine other features, such as hotspots, which are a mid-plate phenomenon that includes the Hawaiian Islands chain.
7.
The Plunging Sea Floor and Deep-Sea Trenches
|
25.
Coastal Erosion—Beaches and Sea Cliffs
Coastlines are constantly changing features. Examine what happens when structures are built to halt or reverse the change, especially at a time when sea level is rising. Most human-engineered solutions turn out to be short-term at best, and many have unintended consequences.
25.
Coastal Erosion—Beaches and Sea Cliffs
|
8.
The Formation of the Earth and Its Ocean
Cover 9 billion years of cosmic history—from the big bang, to the accretion of the sun and planets, to the formation of Earth's oceans 4 billion years ago. The water in the oceans came from water vapor in volcanic eruptions and possibly from comet impacts.
8.
The Formation of the Earth and Its Ocean
|
26.
Tidal Life, Sea Forests, and Coral Reefs
Begin your survey of the organisms and ecosystems that flourish in the most complex and varied part of the ocean: the benthic zone, or sea bottom. Start in the shallows, where life inhabits a wide range of niches—from the crashing waves of tide pools to placid mudflats.
26.
Tidal Life, Sea Forests, and Coral Reefs
|
9.
The Early Ocean and the Origins of Life
Explore scenarios for the origin of life, which may have begun around deep-sea hot springs. The oceans have maintained roughly the same conditions over the entire history of life on Earth, even though the sea floor has renewed itself many times over through plate tectonics.
9.
The Early Ocean and the Origins of Life
|
27.
Deep Bottom Life and Hydrothermal Vents
Continue your investigation of the benthic zone by exploring the deep ocean bottom, where astonishing diversity exists in cold, darkness, and high pressure. Your tour includes sea cucumbers, brittle stars, herds of sea pigs, and the unique community around deep sea vents, which extracts energy from the Earth itself.
27.
Deep Bottom Life and Hydrothermal Vents
|
10.
Marine Sediments—Archives of the Ocean
Ocean sediments are like tree rings that can be "read" as a history of the ocean and climate through time. Investigate the different sources of sediments, which range from products of erosion on land, to the remains of sea creatures, to ejecta from asteroid impacts.
10.
Marine Sediments—Archives of the Ocean
|
28.
Trade Winds—The Circulation of Heat and Wind
Explore another ocean—the ocean of air—which interacts with Earth's seas through the force of wind on water. Investigate the cause of wind patterns such as the trade winds, westerlies, and polar easterlies. Two crucial factors are uneven distribution of heat and the Coriolis effect due to Earth's rotation.
28.
Trade Winds—The Circulation of Heat and Wind
|
11.
Offshore Oil and Gas—Resources and Risks
Learn the origin of petroleum and natural gas deposits, which formed under very specific conditions in marine sediments. As an example of the challenges of oil recovery, survey the technology of deep-water drilling, focusing on the disastrous blow-out in the Gulf of Mexico in 2010.
11.
Offshore Oil and Gas—Resources and Risks
|
29.
Heavy Weather—Storms and Hurricanes
Gain insight into the world's largest storms by looking at the interaction of ocean, atmosphere, and land, and how it produces nor'easters, monsoons, and hurricanes. Focus on the life cycle of hurricanes—how they form, intensify, and often produce devastating storm surges, as happened during Hurricane Katrina.
29.
Heavy Weather—Storms and Hurricanes
|
12.
The Enduring Chemistry of Seawater
Why is the sea salty? Why isn't it getting saltier? Probe these and other mysteries of ocean chemistry, looking at the remarkable stability and uniformity of seawater over time. Also study the role of water and the conjectured role of life in driving plate tectonics.
12.
The Enduring Chemistry of Seawater
|
30.
The Gulf Stream to Gyres—Vast Surface Currents
Follow the chain of events that initiate surface currents in the ocean. Big currents such as the Gulf Stream are caused mainly by wind friction. The mapping of currents has been aided by incidents such as the accidental spill of thousands of floating bath toys in the Pacific in 1992.
30.
The Gulf Stream to Gyres—Vast Surface Currents
|
13.
How the Physics of Water Controls the Ocean
Analyze the surprising properties that keep the ocean liquid and make water the defining physical substance for life. Among them is its ability to retain heat, which has kept Earth in a narrow temperature range hospitable to life for billions of years. Also investigate the propagation of light in water and why the ocean is blue.
13.
How the Physics of Water Controls the Ocean
|
31.
Upwelling, Downwelling, and El Niño
Winds drive surface currents, and together wind and currents set in motion large-scale upwelling and downwelling. Study these patterns and the disturbances that lead to El Niño and La Niña cycles, which cause major disruptions in fisheries and weather.
31.
Upwelling, Downwelling, and El Niño
|
14.
Waves—Motion in the Ocean
Chart the dynamics of wind-generated waves, which include almost all ocean waves. See how they form, grow in size, travel for thousands of miles, and then break on shore. The big waves preferred by surfers come from remote regions that have the ocean's stormiest weather.
14.
Waves—Motion in the Ocean
|
32.
The Deepest, Slowest River—Polar Bottom Water
While surface currents move a typical water molecule around an ocean basin in a year or two, down deep water circulates much more slowly, taking hundreds to thousands of years to make a circuit. Trace how dense, cold water masses from the polar regions slowly but inexorably move the great bulk of the ocean.
32.
The Deepest, Slowest River—Polar Bottom Water
|
15.
Rogue Waves and Tsunami
Long considered a mariners' tall tale, abnormally high "rogue" waves are now well documented. Understand the physics of why they form and the yearly toll they take on shipping. Then study tsunami, or seismic sea waves, which are generated when undersea earthquakes displace huge volumes of water, often with catastrophic results.
15.
Rogue Waves and Tsunami
|
33.
The Ocean and Global Climate
The ocean contains most of the heat in the ocean-atmosphere system, and surface currents distribute it around the planet. Begin your study of the ocean's reaction to increasing carbon dioxide in the atmosphere, which is leading to climate change worldwide.
33.
The Ocean and Global Climate
|
16.
Tides in Theory and Practice
Tides are caused by the gravitational attraction of the moon and, to a lesser extent, the sun. Learn that the timing and height of tides are far more complex than the daily motions of the moon and sun suggest—due to the influences of coastal features, the Coriolis effect, and other factors.
16.
Tides in Theory and Practice
|
34.
The Warming, Rising Sea
Learn that one conjectured effect of global warming—the shutting down of the Gulf Stream leading to a new ice age in Europe—is unlikely. But the planet is already on a path to melting glaciers and steadily rising seas, with catastrophic implications for low-lying populated areas.
34.
The Warming, Rising Sea
|
17.
Marine Life, Energy, and Food Webs
Trace the path of energy and food through oceanic ecosystems, which have a far higher turnover of biomass than the terrestrial equivalents. As a result, most of what grows in the oceans is very quickly consumed. Learn why warm, temperate seas are often nutrient-poor compared with polar waters.
17.
Marine Life, Energy, and Food Webs
|
35.
Marine Pollution—The Impact of Toxins
Turn to the problem of marine pollution, which includes runoff from land and deliberate dumping, in addition to acidification from atmospheric carbon dioxide. Also look at the Great Pacific Garbage Patch, where plastic particles and other debris have concentrated in a rotating mid-ocean current.
35.
Marine Pollution—The Impact of Toxins
|
18.
Tiny Plankton—The Most Abundant Life on Earth
Survey some of the many species of plankton, which are passive, floating, and drifting organisms. Microscopic plankton are ubiquitous throughout the oceans and represent all three of the basic biological domains: Archaea, Bacteria, and Eukarya.
18.
Tiny Plankton—The Most Abundant Life on Earth
|
36.
The Future Ocean
Finish the course by looking into the future. Constant change will continue to be the state of the ocean, just as it always has been. But humans can promote change for the better in a variety of ways, including using the national park model to establish marine sanctuaries. Learn other choices you can make to help preserve this wonder of the planet.
36.
The Future Ocean
|