The Republic of China Yearbook 2009

CHAPTER 1 Geography

Taiwan Proper

Off the eastern coast of Asia lie the mountainous island arcs of the Western Pacific. Taiwan proper is part of the arc that lies closest to the continent and marks the edge of the Asiatic continental shelf. The island is the largest body of land between Japan and the Philippines. Measuring nearly 400 kilometers from north to south and around 145 kilometers from east to west at its widest, it constitutes 99 percent of the area under the nation’s jurisdiction.

Taiwan proper can be divided into five major physiographical regions: mountain ranges, volcanic mountains, foothills, tablelands, and coastal plains and basins. Lying along a seismic belt, the island’s most prominent geological characteristics are the result of tectonic movement. The mountain ranges that run down the center of Taiwan constitute a large tilted fault-block, and in the east of the island, a longitudinal fault valley stands between this fault block and the Pacific Ocean. The slopes of the block’s western flank descend gradually, giving way to fertile coastal plains where agriculture, industry and the bulk of the population are concentrated.

The shoreline of Taiwan proper is largely unbroken, and coral reefs are found around the island’s southernmost tip as well as off Taitung County in eastern Taiwan.

Mountain Ranges

Taiwan’s five longitudinal mountain ranges, which are mostly forested, occupy nearly half of the island. There are more than 200 peaks rising higher than 3,000 meters above sea level, making for some of Taiwan’s most dramatic scenery. In addition, steep mountains over 1,000 meters high constitute about 31 percent of the island’s total land area. As a group, the mountain ranges extend 330 kilometers from north to south, almost the full length of the island, and an average of about 80 kilometers from east to west. The highest peak in Taiwan—and in Northeast Asia—is Jade Mountain at 3,952 meters.

Extending down the eastern half of Taiwan proper, the Central Mountains serve as the island’s major watershed. The range is mostly composed of hard rock formations resistant to weathering and erosion, although in some parts, heavy rain has prevailed and scarred mountainsides with gorges and sharp valleys. The Xue Mountains lie to the northwest of the Central Mountains, gaining in elevation as they extend southward. Named after their highest peak, the Jade Mountains run along the southwestern flank of the Central Mountains. To their west are the Alishan Mountains, with elevations of between 1,000 and 2,000 meters, while the East Coast Mountains consist chiefly of large hills.

Volcanic Mountains

Small outcrops of igneous rock are scattered across the island, representing at least five periods of igneous activity. While Taiwan’s many volcanoes are either dormant or extinct, geothermal activity has produced numerous hot springs across the island. Reputed for their therapeutic properties, the springs attract tens of thousands of foreign visitors each year. The Datun Mountain area, known for its hot springs and fumaroles, is a prominent group of 1,000-meter-high volcanic peaks between Keelung Port and the Danshui River that overlook Taipei.

Foothills

The island’s foothills run in a narrow band around the central mountain ranges, widening in the west. Their topography includes low hills, longitudinal valleys and broad fault scarps. The western foothills are relatively rich in coal and oil. Intersected by three major rivers—the Dajia, the Dadu and the Zhuoshui—the region between Fengyuan (north of Taichung) and Nantou is the widest section of foothills and includes the Sun Moon Lake Basin that lies 765 meters above sea level. Prominent foothills in southern Taiwan include the Chiayi-Pingtung belt and the Hengchun foothills, which occupy most of the Hengchun Peninsula.

Tablelands

Below the foothills, Taiwan’s terrain gradually slopes down into tablelands at elevations of between 100 and 500 meters. These are thick deposits of sandstone gravel that were formed by eroded material washed down from higher areas, though some gravel beds may have been deposited near the sea before being raised up into flat-topped tablelands by recent tilting. The broadest tableland is the Taoyuan Terrace in northwest Taiwan, followed by the Houli Terrace in Taichung, the Dadu and Bagua terraces in Changhua, and the Hengchun Terrace in the south.

Coastal Plains and Basins

The foothills and tablelands merge into broad alluvial plains sitting at an average altitude of less than 100 meters above sea level. Composed mainly of gravel, sand and clay, these plains endow Taiwan with a larger proportion of arable level land than that of either Japan or the Philippines. The shore of the western plain, which faces the Taiwan Strait, is marked by wide tidal flats. Here, shore currents have built up a series of spits and sandbars, and many lagoons have been created through shoreward shifting of the sandbars. All of the larger rivers running through the plains have their sources in high mountains. As they emerge from the foothills, they diverge into smaller channels that meander toward the ocean, forming large alluvial deltas. Many of these rivers and streams have been linked by irrigation and drainage canals.

The vast Jianan Plain in southwestern Taiwan extends from Changhua in central Taiwan to Kaohsiung in the south and accounts for 12 percent of Taiwan’s total land area. Next largest are the Pingtung Plain in the south and the Yilan Plain in the northeast. There are two major basins in Taiwan, the Taipei Basin and the Taichung Basin. Over in eastern Taiwan, the narrow East Longitudinal Valley sits about 120 meters above sea level.

As part of the large-scale i-Taiwan 12 Projects, between 2009 and 2012, the government is carrying out a program to reinvigorate coastal regions by rejuvenating woodlands and promoting recreation and tourism. In addition to developing green corridors, each year, 70 hectares of coastal forest will be rejuvenated and at least 10 fishing ports modernized.

Rivers and Lakes

There are 151 rivers and streams in Taiwan. The Zhuoshui River in central Taiwan is the longest (187 kilometers), while the Gaoping River in the south has the largest drainage basin (3,257 square kilometers). As the Central Mountains are Taiwan’s main watershed, most rivers and streams flow either eastward or westward. They are generally short and steep, especially in the east, and can become torrential during rainstorms, when they carry large amounts of mud and silt. Due to the rapid flow of rivers, water resources can be scarce despite abundant rainfall (see “Climate” on the following page). In the plains, riverbeds tend to be wide and shallow, creating challenges for the management and development of water resources.

Most of Taiwan’s lakes are located in the west, and many are used as reservoirs. Sun Moon Lake in Nantou County, with an area of eight square kilometers and a depth of 30 meters, is the island’s largest and deepest lake. The next-largest lakes on the island are Longluan Lake on the Hengchun Peninsula and Liyu Lake in Hualien County, both of which have an area of around one square kilometer. There are also a dozen alpine lakes in the Xue Mountains and the Central Mountains. The highest among them, Jiaming Lake in the southern Central Mountains, was formed in a meteor crater.

Flora and Fauna

Taiwan’s tropical-to-temperate spectrum of climatic zones and contrasting topographies have endowed the island with a rich diversity of flora and fauna. Some 80 species of mammals, 500 species of birds, 80 species of reptiles, 37 species of amphibians, 3,050 species of fish and 18,000 identified species of insects (including around 400 butterfly species) are known to inhabit Taiwan. The island’s abundant plant life includes 640 species of ferns, 3,510 species of angiosperms and nearly 30 species of gymnosperms.

According to the Council of Agriculture (COA), around 27 percent of the 4,200 or so vascular plant species and over 60 percent of the animal species (including mammals, birds, amphibians, reptiles, fish and insects) found on the island are endemic to Taiwan. A research institute was established in 1992 to ensure the conservation of these species.

Perhaps the most well-known Taiwanese species of fauna is the Formosan landlocked salmon. It is believed to have become trapped in the frigid mountain waters of central Taiwan during the last Ice Age, when ocean levels dropped dramatically and the salmon could no longer migrate between fresh and salt water. Overfishing and pollution have damaged much of the salmon’s natural habitat and shrunk the distribution and population dramatically. In 1989, the COA listed the fish as an endangered species in accordance with the Wildlife Conservation Act, and in 1997, the Taichung County Government established the Formosan Landlocked Salmon Refuge in the upper reaches of the Dajia River in Shei-pa National Park.

Climate

Situated off the east coast of Asia and in the path of warm ocean currents, Taiwan generally enjoys an oceanic and subtropical monsoon climate. Summers are long with high humidity, while winters are short and usually mild. Frost is rare in the lowlands where most of the population is concentrated, and mean monthly temperatures range from 15 to 20 degrees Celsius in winter to around 28 degrees Celsius in summer. The highest and lowest urban temperatures were recorded in Taitung (40.2 degrees Celsius in May 2004) and Taichung (-1.0 degree Celsius in February 1901). In the past 100 years, the surface temperature has increased by about 1.4 degrees Celsius, more than twice the global mean (0.6 degree Celsius).

Taiwan’s annual weather patterns are strongly influenced by the East Asian monsoonal flow. The winter monsoon lasts from October to late March and brings steady rain to northeastern Taiwan, while the central and southern parts of the island experience mostly sunny winters. Many of Taiwan’s offshore islands are buffeted by powerful winds during this time. The summer monsoon begins with the “plum rain” season (so named as it coincides with the plum season) in May and June and usually ends in late September. During this period, the south experiences high levels of precipitation while the north remains comparatively dry.

As Taiwan lies close to the tropical cyclone formation zone in the Western Pacific, summer months are also marked by frequent thunderstorms and typhoons, with an average of three to four typhoons hitting Taiwan each year. Though the strong winds and heavy rainfall that typhoons bring often inflict severe damage, the storms are also a significant source of water, and windward mountain slopes can receive as much as 300 millimeters of rainfall in 24 hours. In 2008, four typhoons made landfall on Taiwan’s eastern coast.

Mean annual rainfall on Taiwan proper is approximately 2,500 millimeters. Southern Taiwan receives 90 percent of its rainfall between May and October. Precipitation is more even in the north, with 60 percent falling between May and October. Throughout Taiwan, November to February is the driest period.

Special Weathers of Taiwan

Although Taiwan is located in the subtropics, in winter, cold fronts from Siberia often drive temperatures to below 10 degrees Celsius and high mountains even receive snow. In summer, however, due to the influence of the subtropical Pacific high-pressure system, temperatures frequently rise to 35 degrees Celsius and above. The island’s mercurial weather patterns are further complicated by the Central Mountains. Three of Taiwan’s unusual meteorological phenomena are described below.

• Burning wind
  This phenomenon sometimes occurs in Taitung County of eastern Taiwan. As wet air arriving in western Taiwan from southern parts of the Chinese mainland ascends over the Central Mountains via orographic lift, the water vapor in the air condenses to form clouds that bring rain to the windward side. The remaining dry air moves over the mountains and descends on the leeward side, warming in an adiabatic compression process. The result is a wind that reaches high temperatures at the lower altitudes akin to the Alpine foehn and the Rocky Mountain chinook.
• Downslope wind
  A downslope wind occurs when an east wind passing over the southern Central Mountains speeds down the western slopes to Hengchun in Pingtung County. Unlike the burning wind, the temperature of this fall wind does not rise. If anything, it brings a cooler temperature to Hengchun. Generally manifesting during the northeast monsoon in winter, these gales can reach force 13 on the Beaufort scale.
• Northwest rains
  These short-lived air-mass thunderstorms, which can make a sudden appearance on summer afternoons, are the result of radiation heating of the sun. Though northwest rains can cover dozens of square kilometers, they often affect areas as small as one or two square kilometers. As a local saying goes: “The northwest rain doesn’t fall beyond the edge of the field.” Rainfall is short, generally lasting between a few minutes and one hour. Taipei at times can experience northwest rains on several successive afternoons, with each rainfall commencing progressively earlier or later than on the preceding day.

Earthquakes

Taiwan experiences relatively frequent seismic activity due to its location on the circum-Pacific seismic belt and at the junction of the Manila and Ryukyu trenches along the west side of the Philippine Sea plate (PSP). Geologists have identified a total of 42 active faults on the island. According to the Central Weather Bureau, from 1994 to 2008, about 20,000 earthquakes occurred annually in the Taiwan area, of which around 1,000 were felt by people each year.

The PSP and the Eurasian plate (EUP) converge at a rate of about seven to eight centimeters per year. This convergence, which created the uplift that formed Taiwan’s Central Mountains, continues to subject most of the island to northwest-southeast compression. East of Taiwan, the PSP subducts northward beneath the EUP, while to the south of the island, the EUP underthrusts eastward beneath the PSP. Seismic activity in northeastern and southern Taiwan is associated with these two subduction zones.

In central and western Taiwan, earthquakes are less frequent, of a smaller scale and with shallower focal depths. There was one exception to this, however, on September 21, 1999, when a major earthquake occurred near Jiji Township in Nantou County, about 150 kilometers south of Taipei, registering 7.3 on the Richter scale. It was the largest seismic event to affect Taiwan in the 20th century.

Penghu

Comprising 64 islets, the 126.9-square kilometer archipelago of the Penghu Islands (at times called the Pescadores) is located near the middle of the Taiwan Strait. The islands act as a natural demarcation between the East China Sea and the South China Sea and, in the past, were an important stopping point for ships operating in the Far East or traversing the Pacific. They are formed mostly of basalt and have relatively flat terrain resulting from long-term erosion. The highest point on the archipelago is on Mao Island at 79 meters above sea level. The residents of Penghu County benefit from some arable land on the three main islands, but there are no rivers. Winding coastlines form numerous natural harbors, and warm, shallow coastal waters favor the growth of coral.

The mean temperature in Penghu County is 22.7 degrees Celsius and annual rainfall, at about 1,000 millimeters, is far below Taiwan’s average. Further, evaporation rates in the area are high due to strong winds, and guaranteeing sufficient water supplies is therefore a top priority. There are a total of seven reservoirs, one of them underground, and most households have their own wells.

Only 19 of the Penghu Islands are inhabited, with over 70 percent of the population living on Penghu proper, the largest island in the archipelago. The two other main islands, Xiyu and Baisha, are connected by causeways as well as by the longest inter-island bridge in East Asia, the Cross-sea Bridge.

Kinmen

The 12 islands of Kinmen (also known as Quemoy), 150.5 square kilometers in area, are situated just off the southeastern coast of mainland China’s Fujian Province. Blocking the mouth of Xiamen Bay, they are a highly strategic military location in the Taiwan Strait. The shortest distance between the main island of Kinmen and mainland China is just 2,310 meters. Kin-men has a mean temperature of 20 degrees Celsius and an average annual rainfall of about 1,200 millimeters (2004-2008).

Though its satellite islets are low and flat, Kinmen Island itself is hilly, with Taiwu Mountain’s summit being the island’s highest point at 253 meters. Most of Kinmen’s rivers are short and narrow with unsteady flows, and reservoirs have been constructed to ensure an adequate water supply. Zigan Port, located in Liaoluo Bay on Kinmen Island’s southern coast, is deep enough to accommodate ships of several thousand tons.

Matsu

Matsu is a minor archipelago of 36 rugged islands, 28.8 square kilometers in area, located at the mouth of mainland China’s Min River, less than one kilometer from the mainland’s coast and more than 210 kilometers from Keelung in northern Taiwan. The islands are collectively administered as Lienchiang County.

With an area of 10.4 square kilometers, Nangan is the largest and most populous island. There are two harbors in Nangan— Fu-ao and Matsu. Other major islands of the group include Beigan, Gaodeng and Liang Island. The Matsu Islands were formed by an uplift of igneous rock, and granite is the main natural resource. The mean temperature here is 18.6 degrees Celsius, while average annual rainfall is around 1,168 millimeters (2004-2008).

Although the archipelago’s hilly terrain is not naturally suited to agriculture, 16 reservoirs have been constructed and 320 irrigation wells drilled to facilitate farming. This has enabled Matsu to become self-sufficient in vegetable production.

Other Islands

Green Island and Orchid Island are two hilly, volcanic islands located off the Pacific coast of Taiwan. Situated 33 kilometers east of Taiwan proper and with an area of approximately 15 square kilometers, Green Island is home to one of the world’s three saltwater hot springs, Zhaori Hot Springs. Orchid Island, which is inhabited by the indigenous Yami people and lies 83 kilometers off the southeast coast of Taiwan, has an area of 47 square kilometers, making it Taiwan’s second-largest offshore island after Penghu. Coral reefs and abundant sea life fringe the coastlines of both islands.

Sitting just off the southwest coast of Taiwan proper, Xiaoliuqiu is one of the largest coral islands in the world at 6.8 square kilometers. The unique coral formations found here were created by eons of wind and rain erosion. Much of the coral is a brilliant crimson as it is composed primarily of iron and silicon oxides.

Further, the ROC maintains a historical claim to four groups of islands scattered over a vast area in the South China Sea. These are the Dongsha (Pratas) Islands, the Nansha (Spratly) Islands, the Xisha (Paracel) Islands and the Zhongsha Islands (Macclesfield Bank). Currently, Taiwan’s effective jurisdiction includes the Dongsha Islands, as well as Taiping Island and Zhongzhou Reef of the Nansha Islands.

The Dongsha Islands are located 444 kilometers southwest of Kaohsiung and comprise Dongsha Island—a coral atoll with an area of 2.38 square kilometers— and two coral reefs. In addition to being a source of fish and minerals, the islands are used as a coast guard outpost. A hospital, a power station, a satellite tracking facility and a runway have also been built on Dongsha Island.

Boasting abundant fishing, mineral and petroleum resources, the Nansha Islands comprise more than 190 islets, reefs, cays and banks spread out over an area extending 810 kilometers from north to south and 900 kilometers from east to west. Taiping Island, located 1,384 kilometers southwest of Kaohsiung, is the largest island in the group with an area of 0.49 square kilometer. The Coast Guard Administration has stationed personnel on Taiping Island, which received a new runway in 2008.

In keeping with the ROC’s peaceful intentions, the Dongsha Islands, Taiping Island and Zhongzhou Reef have been transferred from military to civilian rule. In 1999, responsibility for defending these islands passed from the Ministry of National Defense to the Coast Guard Administration, while the administration of these islands was handed to the Kaohsiung City Government.

Finally, lying about 170 kilometers northeast of Taiwan proper is the Diaoyutai Archipelago, a tiny island group that includes Diaoyutai Island, Huangwei Islet and Chiwei Islet.