Mountains

Environmental Issues, Global Perspectives

James Fargo Balliett

• Publisher: Routledge
• Year: 2016
• Print ISBN: 9780765682284
• eBook ISBN: 9781315496993
• Topic: Biological Sciences
• Subtopic: Economic Theory
• Index: Biological Sciences

Always awe-inspiring, mountainous areas contain hundreds of millions of years of history, stretching back to the earliest continental landforms. This book shows how mountains are characterized by their distinctive geological, ecological, and biological conditions. Often, they are so large that they create their own weather patterns. They also store nearly one-third of the world's freshwater—in the form of ice and snow—on their slopes. Despite their daunting size and often formidable climates, mountains are affected by growing local populations, as well as distant influences, such as air pollution and global climate change.

Three detailed case studies are presented. The first shows how global warming in East Africa is harming Mount Kenya's regional population, which relies on mountain runoff to irrigate farms for subsistence crops. The second examines the fragile ecology of the South Island Mountain in New Zealand's Southern Alps and how development threatens the region's endemic plant and animal species. The third discusses the impact of mountain use over time in New Hampshire's White Mountains, where management efforts have been used to limit the growing footprint of millions of annual visitors and alpine trekkers.

Introduction to Mountains

1

Mountains’ Majesty

Few landforms on Earth are as impressive as massive mountains. In fact, their towering presence has inspired and influenced the belief held by many cultures that mountain peaks were formed and are occupied by gods. These giant landforms feature distinctive geological, ecological, and biological conditions in some of the planet’s most remote places.

Mountains contain multiple distinctive climates, are comprised of dangerous surfaces (from steep pitches to glaciers and active volcanoes), and are so large that they create their own weather patterns. Most mountain climates are colder than those at lower altitudes due to their height, and water in and above the ground may remain frozen either year-round or for most of the year.

Due to their daunting size and often formidable climate, mountains have served as almost impassable dividing lines between some countries and also can isolate wildlife. Related plant and animal species separated by mountain ranges gradually go through what is called allopatric speciation (when geographic isolation results in a separate reproductive genetic pool of the species); this can result in varied evolution over millions of years.

The isolated ecosystems on a mountain often are fragile, due to the species that have lived and evolved within its commonly isolated, high-altitude boundaries. Once a mountain area is damaged by pollution, it takes several times as long to be restored. Garbage accumulation, mining tailings, oil spills, sedimentation, and untreated human waste are a few types of pollution that threaten the ecological health of mountains.

The Black Hills stand out among the Great Plains of South Dakota and Wyoming. The name of these domed mountains, translated from the Lakota Pahá Sápa, refers to the fact that they generally appear dark when seen from a distance. (© Robert Gil/Fotolia)

Mountain regions contain up to 80 percent of the planet’s freshwater and many natural resources such as gas, minerals, metals, stone, and wood. Although remote mountain locations are difficult to access due to their limited infrastructure (such as roads), isolated geography, high altitudes, and steep conditions, new technology and demand for mountain resources often drive commercial enterprises and governments to venture into these regions.

In one such example, the Chinese government finished a $4 billion train route through a section of the Himalayan Mountains in 2006, connecting mainland China with Tibet. This 710-mile (1,143-kilometer) route between Lhasa and Golmud takes twelve hours to complete and climbs high into the Himalayas, including the 16,640-foot (5,072-meter) Tanggula Pass.

The project required miles of rock removal, installation of 170 new structures such as bridges and tunnels, a set of three specially built diesel engines, and oxygen masks provided to passengers to help them bear the high altitudes. Although persistently low temperatures, snow and rock slides, and high winds threaten this rail line, Chinese officials say that the government is committed to maintaining year-round access into previously remote Tibet.

Mountains Defined

A mountain is composed primarily of rock shaped over time by geologic forces such as tectonic plate movements and volcanic eruptions. Mountains typically have steep sides, a narrow peak, and a defined base.

Although they stand thousands of feet above their surrounding landscape, they are temporary structures. Weathering from wind, water, cold and hot air, and chemicals slowly reduces a peak from as high as Mount Everest at 29,028 feet (8,848 meters) to a few thousand feet after millions of years. The full cycle of mountain building and erosion takes hundreds of millions of years. Some mountains, such as the Urals, Rockies, and Appalachians, are so old that they have experienced three or four building and erosion cycles.

The Earth is roughly 4.6 billion years old. One billion years after it formed, the first mountain ranges were created from cooling lava flows. With an average diameter of 7,913 miles (12,734 kilometers), the planet is constructed of three concentric layers: a core (from 3,954 to 1,790 miles, or 6,363 to 2,880 kilometers, deep); a mantle (from 1,790 to 22 miles, or 2,880 to 35 kilometers, deep); and a crust (22 miles, or 35 kilometers, or less deep).

The core, at the center of the Earth, is made of mostly solid iron and nickel. Surrounding the core is the mantle, which is comprised of partially molten rock and lava. The last layer, the crust, sits on the outer surface of the planet, on top of a partially molten layer called the lithosphere, ranging from 180 to 70 miles (289 to 113 kilometers) thick.

The crust is made up of fifteen major and forty-one minor tectonic plates that cover the Earth like a jigsaw puzzle. These plates span a total surface area that is 196,937,429 square miles (510,065,599 square kilometers) in size, including both land that is under water (rivers, lakes, and oceans) and dry land. Of that surface

TALLEST MOUNTAINS AROUND THE WORLD
Location	Mountain	Height (Feet)	Height (Meters)
Africa	Mount Kilimanjaro	19,340	5,895
Antarctica	Vinson Massif	16,066	4,897
Eurasia	Mount Everest	29,028	8,848
North America	Mount McKinley	20,320	6,194
Oceania	Puncak Jaya	16,503	5,030
South America	Aconcagua	22,834	6,960

area, 29 percent, or 57,511,026 square miles (148,952,873 square kilometers), is dry land; 24 percent of that land consists of mountains.

Mountains are formed by several different methods, the most common of which is the collision of two tectonic plates. This violent action results in a number of folds in the surface of the Earth, as opposing sections of bedrock collide, and eventually the less dense material collapses into layers. The effects of the impact of two or more plates continue over millions of years. For example, when the Indian-Australian Plate moved northward into the Eurasian Plate 70 million years ago, the collision began the process of forming the Himalayan Mountains.

Mountains also are formed when lava pushes up through a weak spot between two tectonic plates, and this high-pressure eruption creates a landmass. Twenty million years ago, this is how the mountains across Iceland were created.

When does a hill become a mountain? Most landforms are considered mountains when they are higher than 1,000 feet (304 meters). Mountains are measured by their height above sea level; however, many mountains form on the sea floor. For example, Mauna Kea in Hawaii is recorded as 13,796 feet (4,205 meters) high, but it is really more than 32,000 feet (9,754 meters) tall, because more than 18,000 feet (5,486 meters) are submerged in the Pacific Ocean.

The highest mountain on the planet is Mount Everest. It is 29,028 feet (8,848 meters) tall and sits within the Himalayas at the border between the countries of China, Tibet, and Nepal. Although mountains take up nearly one-quarter of the planet’s landmass, only 3 percent of Earth’s surface rises above 6,500 feet (1,981 meters).

Mountain Ranges

While there are thousands of individual mountains across the globe, mountains can be broken down into two major chains, as well as a half dozen noteworthy ones.

The first major group of mountains consists of a combination of the Himalayas, the Alps, and the Atlas Mountains, which run through parts of Europe, North Africa, and Asia. The second massive chain is made up of the Rockies and the Andes, and it stretches from the top of North America to the bottom of South America and into Antarctica. Both mountain chains were formed roughly 50 million years ago.

A number of smaller ranges exist in other locations. These include the Appalachians in the eastern United States, the Ural Mountains in northern Russia, the East African Highlands in eastern Africa, and the Snowy Mountains in northern Australia.

MOUNTAIN COVERAGE ON EARTH
Continent	Coverage (Percent)
Africa	25
Antarctica	32
Asia	54
Australia	17
Europe	25
North America	36
South America	22

There are five different types of mountains: the dome, fold, fault-block, volcanic, and plateau. Each type has unique physical features resulting from its geologic origin. These form in a process known as orogeny, a Greek word meaning “mountain building.”

Dome Mountain

A dome mountain is formed when molten rock pushes from underneath the Earth’s crust and forms a slab of sedimentary rock into a rounded shape. Instead of a towering eruption, layers of lava accumulate over several years to create a dome shape. Erosion then carves away at the exterior, forming valleys and sharper peaks.

The base of a dome mountain may be more than 100 miles (161 kilometers) in diameter. An example of this mountain type is the 7,388-foot (2,251-meter) Black Dome Mountain in British Columbia, Canada.

Fold Mountain

A fold mountain is formed when two tectonic plates collide, folding their layers into each other to create a larger landmass. In this most common type of mountain, the folded layers have been subjected to great stress and are susceptible to fracture and erosion.

Geologists were surprised to find evidence of seashells at the top of the Andes Mountains in South America, 100 miles (161 kilometers) from the ocean. But the mystery had a simple explanation: The collision of the Pacific and South American tectonic plates had pushed sections of ocean floor 18,000 feet (5,486 meters) high in a series of folding motions that began 25 million years ago and continue today.

Another example of an older fold mountain range is the Pyrenees Mountains between France and Spain. It was created 200 million years ago during the collision of the African and Eurasian tectonic plates.

Fault-Block Mountain

A fault-block mountain is created in a process called taphrogeny. When two separate sections of tectonic bedrock plate come into contact, the vertical motion results in sections of crust either moving upward or pressing downward. Instead of folding into layers, this crosscut action results in a jagged pattern of varying angles of stacked bedrock. As various pieces of bedrock impact, two noteworthy landforms are created: 1) an upper block, which results in mountains and is called a horst (an old German word meaning “thicket”), and 2) a lower block, which creates lowland, such as a depression or valley, and is called...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• Preface
• PART I. INTRODUCTION TO MOUNTAINS
• PART II. MOUNTAINS OF THE WORLD : CASE STUDIES
• PART III. MOUNTAINS CONCLUSION
• Glossary
• Selected Web Sites
• Further Reading
• Index