Energy, Power, Force, and Pressure

Energy units and their equivalents

joule (abbreviation J); 1 joule = 1 unit of force (a newton) applied over a distance of 1 meter = 0.239 calorie

calorie (abbreviation cal); 1 calorie = heat needed to raise the temperature of 1 gram of water from 14.5 °C to 15.5 °C = 4.186 joules

British Thermal Unit (abbreviation BTU); 1 BTU = heat needed to raise the temperature of 1 pound of water 1 °Fahrenheit from 39.4 to 40.4 °F = 252 calories = 1055 joules

Power

watt (abbreviation W); 1 watt = 1 joule per second

horsepower (abbreviation hp); 1 hp = 746 watts

Force and Pressure

newton (abbreviation N); 1 newton = force needed to accelerate a 1-kilogram mass over a distance of 1 meter in 1 second squared bar (abbreviated b); 1 bar = pressure equivalent to 100,000 newtons on an area of 1 square meter

millibar (abbreviation mb); 1 millibar = one-thousandth of a bar pascal (abbreviation Pa); 1 pascal = force exerted by 1 newton on an area of 1 square meter

atmosphere (abbreviation Atmos.); 1 atmosphere = 14.7 pounds of pressure per square inch = 1013.2 millibars

Length, Area, and Volume

Length 1 micrometer (μm) = 0.000001 meter = 0.0001 centimeter

1 millimeter (mm) = 0.03937 inch = 0.1 centimeter

1 centimeter (cm) = 0.39 inch = 0.01 meter

Chapter Overview

The atmosphere is a complex system, sometimes described as chaotic in nature. In this chapter we examine one of the principal components of that system, the precipitation system, and find that it is indeed complex, but within that complexity, there is a good deal of order to be found in its processes and patterns. We want to learn how precipitation is produced and how and where it is delivered. We trace our way through the atmospheric moisture system, beginning with a brief examination of water vapor, humidity, and condensation and then go on to the processes and causes of precipitation and their geographic circumstances, including the nature of storm systems such as thunderstorms, tornadoes, and hurricanes. The chapter ends with some insights into the nature of violent storms and some of their consequences.

Introduction

The town was nothing more than a general store and saloon on a side road a few hundred feet off US-21 in northern Nebraska. A half mile or so to the north you could see a few houses and beyond them endless farm fields and plains stretching into the horizon. Thunderstorms with great billowing heads dominated the hot afternoon sky creating shadowy islands in an otherwise sunny landscape. Inside the store we milled around looking at antiques and chatting with the clerk. Suddenly, a siren sounded. Almost immediately the clerk said, “It's a severe storm warning, probably a thunderstorm, we get them all the time.”

Chapter Overview

This chapter takes us into the solid Earth and the system of forces that shapes the Earth's crust, the platform of rock upon which the landscape and the oceans rest. This is important to physical geography for crustal processes and features exert a powerful influence on surface systems including oceanic and atmospheric circulation, climate, biogeography, and even the location and operation of watersheds. The story begins in the Earth's interior, the source of energy that powers the crustal processes like volcanoes and earthquakes, and how that energy makes its way toward the planet's surface. To answer this question, it is helpful to take a brief look at Earth's early formation as a planet. This will explain Earth's gross composition and structure and how the internal energy system is constructed. We then go on to examine how the great internal energy system works, how it brings heat to the surface and causes the crust to break apart and move in great sections called tectonic plates.

Introduction

All the great systems that we have discussed so far in this book, including the hydrologic cycle, atmospheric pressure and winds, ocean circulation, and ecosystems, are powered by solar radiation. It is now time to look inside the Earth and examine the system driven by Earth's internal energy system. The term traditionally given to this source of energy is endogenous, that is, having origin within the planet.

Chapter Overview

Mark Twain warned that we risk losing touch with the romance and beauty of a river by knowing about and attaching meaning to its parts. It appears that is a risk we will have to face in this chapter as we go in search of answers to some big questions about streams, beginning with why are they so effective in lowering the landmasses and shaping landscapes? Part of the answer has to do with their geographic coverage. They are one of Earth's most ubiquitous terrestrial features, operating in humid and dry and mountains and flat terrains alike. Part also has to do with the fact that they are organized into great branching systems, large enough to link the interiors of the landmasses to coastal lands and the sea. Accordingly, we begin this chapter with a brief discussion on streams as systems, the nature of streamflow, and the erosional processes of water running in open channels. This is followed by a look at the forms and dynamics of stream channels, how streams cut and shape their valleys, and develop landforms over entire watersheds. Next is a description of some of the grand ideas that have been advanced by scientists over the years to explain how stream systems shape the surfaces of continents. The chapter closes with some remarks about human impacts on stream systems.

Chapter Overview

Again and again we are reminded how critical the atmosphere is to understanding the geographic character of the Earth's surface. In earlier chapters we established that the atmosphere is, among other things, the medium for heat, radiation, and gas exchanges, the source of precipitation and freshwater, and the embodiment of the greenhouse that mitigates thermal extremes and nurtures all life. And now we take one last look at the atmosphere, this time as a geomorphic system, a fluid capable of eroding land, moving sediment and shaping landforms. Like most geographic phenomena, this system operates at several scales, ranging from the very large troposphere to the micro-world of ants on the ground. We explore the behavior of the airflow system with a brief look at wind velocity, direction, and patterns and then venture into wind erosion, sediment transport, and related landforms. The chapter goes on with a description of the processes involved in building and moving sand dunes, the names and the various classes of dunes found in desert and coastal zones, and ends with a review of wind deposits at the global scale and the big question of the relationship of the atmosphere as a geomorphic system to other global systems.

Introduction

Ray looked at the sky, thought for a moment, and said, “We'd best take a ride.” He headed for the car behind the fish house. This was serious. It meant that the storm was getting bad and even these two old fishermen, veterans of howling gales, were hesitant about a trip to the center of Lake Superior.

Chapter Overview

This chapter is about the concept of balance in the Earth energy system. We deal first with the input side of the system by bringing solar radiation into the Earth's atmosphere to see what happens when it passes through air and strikes the Earth's surface. Since geography is our main concern, we are particularly interested in factors, such as cloud cover and the curvature of the Earth, which influence the global distribution of solar energy. Next is the output side of the system. To keep from overheating, Earth must release back into space the energy it gains from the Sun. But before this can take place, solar radiation must be converted into heat and then converted back into radiation in order to leave the atmosphere. We then examine the balance between Earth's energy inflows and outflows. The chapter ends with a look at global temperature patterns and the geographic controls on those patterns, in particular the world distribution of land and water.

Introduction

Uncle Bill could have been a character out of a Jack London novel. At least that's how I, at the age of eight or nine, saw him. On this occasion he was home on Christmas leave from the Air Force and he thought it might be challenging for us to experience a winter night camping out in the northern Michigan woods. But to make it truly challenging, he suggested that we “rough it” by doing without the standard cold weather gear.

Chapter Overview

The Battle of Gettysburg, a pivotal event in American history, was strongly influenced by the lay of the land. But instances of landforms influencing battles and even shaping the development of countries and entire cultures are not unique in the annals of world history. Mountain ranges in particular have influenced where political boundaries are drawn, how religions and languages are distributed, and who trades with whom. So it behooves us to learn about mountains, both their geological and geographical aspects. In this chapter we want to learn first about their anatomies, that is, what do mountains look like on the inside? This will lead to a brief survey of mountain types and how rock is deformed by tectonic forces into folded, faulted, and volcanic structures. The remainder of the chapter is devoted to an examination of the two most studied and feared phenomena of mountain lands, earthquakes and volcanoes, with a glimpse at some of the most notorious of these natural villains including the infamous Mt. Pelee explosion of 1902 that killed 28,000 people, the more infamous Haitian earthquake of 2010 that killed more than 250,000 people, and the East Japan earthquake and tsunami of 2011 that killed over 25,000 people. The chapter ends on the question of the influence of volcanic eruptions on global weather and climate.

Chapter Overview

This chapter opens with a brief look at the biosphere as a physical component of the landscape and oceans and then goes on to examine Earth's bio-energy system. Scientists refer to this system as an ecosystem and all life from bacteria and flies to humans and redwoods is inextricably woven into ecosystems. What drives ecosystems and how do plants convert the energy and matter that fuels them into organic energy and how does that energy get passed along to other organisms? And to make things truly geographical, we must examine how the work of ecosystems is distributed over the globe, and how it all relates to geographic conditions of the atmosphere, land, and sea, such as the distribution of heat and moisture. Finally, where do we humans and the agricultural systems we have put together fit into the global ecosystem?

Introduction

Earth's biological system has been developing for over 3 billion years. It began in the sea with simple, single-celled organisms and evolved into a vast network of plants, animals, and microorganisms that today occupies the entire planet. We call this network of life the biosphere, and although it can seem massive when we stand in a forest or dive into the ocean, it is actually quite thin and tenuous compared to the lithosphere, hydrosphere, and atmosphere. Yet the biosphere is central to Earth's geographic character for, among other things, it is instrumental in shaping soil, climate, hydrology, and the physical character of most landscapes.

Chapter Overview

Our story begins with a brief look at the runoff systems that feed streams. We are particularly interested in the role the landscape plays in these systems and, in turn, in streamflow; for example, how trees intercept rainfall and how soil soaks up rain that hits the ground. We are also interested in how the atmosphere delivers rainfall and how rainfalls of different intensities and durations influence streamflow. All this is set into the geographic framework of a watershed where networks of streams of various sizes and patterns form elegant water-moving systems. And no story about streams would be complete without addressing flooding, a phenomenon that has baffled and plagued humans for thousands of years. The chapter concludes on a distinctly geographic note, an overview of the 20 largest watersheds of the world, which include the Amazon, Mississippi, Nile, and Yangtze.

Introduction

Ancient Hindu and Buddhist mythology describe a sacred mountain at the center of the Universe as the source of the Earth's great rivers. Early Christian mythology identifies the Garden of Eden as the place where Earth's waters divide to form the great rivers. Thousands of years later, in the nineteenth century, we were still speculating on the sources of many great rivers. Scores of explorer/geographers driven by the romance of adventure, scientific curiosity, and political directives ventured into the heart of North America, South America, Asia, and Africa to find the few remaining undiscovered river sources.

If you give our planet a hard poke somewhere, it is apt to set off a chain of reactions leading to change somewhere else, maybe in many places, and often far away. We live in a broadly interconnected geographic environment, one laced with multitudes of systems, a veritable planetary network of wiring and plumbing in three-dimensional space.

These interconnections are astounding. Among them are systems linking temperatures of tropical seas with the size and number of hurricanes that strike midlatitude coastlines, dust storms over the Sahara of North Africa with the fertility of soils in the Amazon Basin of South America, soil erosion on the plains of northern China with the quality of air over Seattle, fertilizer applications on cornfields in Iowa with sick and dying ecosystems on the Mississippi Delta, and earthquakes in Indonesia with giant ocean waves capable of killing hundreds of thousands of people on the other side of the Indian Ocean more than 3000 miles away.

Yet we find it difficult to think in broad patterns and networks because we have learned to see the world in geographic compartments. To physical geography, which is interested in the distribution of natural phenomena, this is a dilemma because it implies that the nature operating in one place may have little or nothing to do with the nature operating in another place. This sort of thinking is reinforced again and again in our lives.

Chapter Overview

Glaciers have became media causes celebres because they are considered harbingers of a changing global climate, and rightly so. To form and survive, glaciers need cold temperatures and plenty of snow, and when one or both of these changes on an established glacier, it grows or shrinks, and lately glaciers the world over have been shrinking not because of too little snow but because of warmer temperatures. And when we look back over the past two million years or so in Earth history, we find concrete evidence of distinct patterns of glaciers growing and shrinking in response to changes in climate. This is meaningful, but equally meaningful is the work of glaciers as geomorphic systems. They have enormous erosional power, so great that they are capable of grinding the sides off mountains. So we also want to learn how they form, grow, move, erode the land, transport rock debris, and shape landforms. We begin with the types of glaciers found in the world and how they originate and function as systems. Next, we look at glaciers as geomorphic agents, first mountain glaciers and then their larger counterparts, continental glaciers. In this connection we are interested in the occurrence of ice ages and their relationship to climate change on Earth.

Introduction

We edged our way onto the ice shelf on Lake Superior's south shore. It was January and a frigid wind bore down on us from the northwest. Along the front of the shelf, about 200 meters offshore, storm waves rammed against the ice sending spray and chunks of loose ice high into the air. As it fell onto the shelf, the spray froze immediately in a slick glaze.

Chapter Overview

Our goal in this chapter is to sketch a picture of atmospheric and oceanic circulation systems at the global scale. We have some big questions to address, beginning with a very basic one: why air is so mobile and what drives its motion? Once we get a handle on why the atmosphere moves, we can examine the basic structure of the atmosphere's circulation, both at the surface and upper troposphere, and reveal how the ancient mariners used this understanding to navigate the Earth. The next step is to learn about the major wind systems such as the prevailing westerlies in the midlatitudes and the easterly tradewinds in the tropics. In the second half of the chapter we move from wind to waves to ocean currents and the big picture of oceanic circulation, noting this system's important role in shaping global climate and how it feeds into the emerging climate-change scenario.

Introduction

Perhaps none of Earth's great systems is more pivotal to understanding the geographic character of our planet than the atmosphere. Indeed, we might think of the atmosphere as the master system among the great systems: first, because it is the main engine driving other great systems, most notably the hydrologic cycle; and second, because it is the vehicle that ties together systems such as the global water and biochemical cycles. Without the atmosphere, the hydrologic cycle and biochemical cycles (such as oxygen and carbon dioxide exchanges) cannot function.

Chapter Overview

Our main objective so far in this book has centered on the systems and processes responsible for the geographic distribution of energy (mainly heat and radiation) and matter (mainly water). Accordingly, this chapter opens with a brief look at the nature of the systems that produce the main ingredients of climate and how they vary in their distributions and behavior, and goes on to examine the two big climate engines, the tropical engine and the midlatitude engine, and how they operate. This is followed by a brief description of a traditional climate classification scheme, which divides the Earth into five main climatic zones. The chapter ends on a practical note: how humans have adapted to climatic conditions through technologies of clothing and shelter.

Introduction

People everywhere brag and whimper about the woes of their early years, but nothing can compare with the Irish version: the poverty; the shiftless loquacious alcoholic father; the pious defeated mother moaning by the fire; pompous priests; bullying schoolmasters; the English and the terrible things they did to us for eight hundred long years.

Above all – we were wet.

Out in the Atlantic Ocean great sheets of rain gathered to drift slowly up the River Shannon and settle forever in Limerick. The rain dampened the city from the Feast of the Circumcision to New Year's Eve. It created a cacophony of hacking coughs, bronchial rattles, asthmatic wheezes, consumptive croaks. It turned noses into fountains, lungs into bacterial sponges.

Chapter Overview

We now examine the types of plants and animals that inhabit Earth and the factors that govern their geographic distributions. These organisms form a great system in which various, and often distant, parts are woven together into complex networks. In terms of sheer mass, the vast majority of these biota is made up of plants whereas most of the species are represented by animals, particularly insects. We will find that many factors govern the distributions of plants and animals, but at the global scale climate and the patterns of land and water, both present and past, are important. On land, smaller scale factors such as regional climate, landforms, drainage patterns, and land use are significant controls. And at an even finer scale, we will see that local factors such as variations in soil and microclimate also play a part.

Introduction

We pushed our way through the brush to the edge of the pond, a simple little basin with the uninspiring name of “Pond 20.” It was built to collect stormwater runoff from an equally uninspiring subdivision with the elegant name of Crown Isle, and we had gone there to check its summer water level. We expected little more than an overgrown mud-puddle, but were pleasantly surprised at what unfolded. Beyond the overhang of the canopy, sunlight penetrated the water, warming the surface layer and amplifying the commotion of various bugs and small fish.

Chapter Overview

The Greek playwright Euripides wrote that a bad beginning makes for a bad ending. Although humans had a tough beginning, after thousands of years better times eventually emerged as people spread over much of the world and adapted to different landscapes. But with technological advances and the pressure of growing population, adaptation changed to more and more serious forms of environmental manipulation. What began with ancient peoples as a cooperative relationship with their geographic environment has now evolved into one characterized more by a desire for control. Could the human drama on Earth have a bad ending? This chapter opens with an interesting geographic puzzle – the African origins of Homo sapiens and our early migration to Asia, Europe, Australia, and the Americas. It then goes on to consider early agriculture, the rise of population centers, the Industrial Revolution, and their effects on the geographic environment. Measured by the last few centuries, the outcome is a rapidly growing imbalance between human systems and natural systems. The chapter ends by offering a big-picture perspective on human activity on Earth in light of the fact that ours is a planet characterized more by geographic change than by stability.

Introduction

Life has profoundly influenced Earth's geographic character. Of that there is absolutely no doubt among geographers. During its evolution life has directly or indirectly caused many big changes in Earth systems, which have in turn led to major transformations in the biophysical and geographic character of the planet.