Unit 1   Geography of Penghu
 
Author: An-Ming Wujng(翁安明)     Translator:Gloria Fung

I.  Origin of the Name “Penghu Islands”

          The Penghu Islands are made up of about one hundred islands and reefs.  In different times in history, it was called “Dao Yi (島夷),” “Si Ying (西瀛),” “Peng Hai (澎海),” Ping Hu (平湖),” etc.  These all refer to the fact that the islands lie to the west of Taiwan, and that while the outer seas that surround them are stormy, the inner seas are calm.

          It is written in the Annals of Penghu County (澎湖廳志), “The word Peng refers not to the sea but to the islands.  The islands are scattered like chess pieces, some farther out and some closer….Magong City is in the centre; its sheltered location makes it the most important of all the islands.  The waters of the harbour are calm and close to a thousand boats can moor there.  Siyu(西嶼) is the outermost buffer; Jinguitoh, (金龜頭)which shields the harbor in the southeast, is the right arm and Shetou(i蛇頭) is the left arm, Big and Small Anshan (大小案山)are the lower arms.  Together, they protect the harbour.  The name Penghu tells us, the waves outside the harbour are tempestuous; but, in the harbour, it is calm as a lake.” This is the origin of the name “Penghu.” 

II. Basalt Columns – The Legend of Black Gold

          Towards the end of the Ming Dynasty, piracy was widespread between the Chinese Mainland and Penghu.  To safeguard his fleet of merchant ships that often crossed the sea between China and Penghu, the richest man in Penghu at the time, Jhang Bai-wan(張百萬), tried many different strategies, but the pirates turned up on his doorstep anyway.  The leader of the pirates told Jhang, “You must hand over your money by tomorrow at noon if you want to keep your life.  However, I will offer you a choice; let’s see who is the richer of the two of us.  If you turn out to have more gold, I will never give you any trouble again.”  The pirate left after delivering his challenge. 

          Jhang thought, “The pirate is sure to be wealthier from all these years of robbing people; I will surely lose.” Just as he was thinking of a solution, he caught sight of the moonlight shining on the wall of his home.  That gave him an idea. 

          The next day at noon, the leader of the pirates stood at the front of his ship while Jhang stood on the shore.  The two men were separated by a hundred feet.  The agreement was they would take turns throwing pieces of gold into the sea; the first one to run out of gold would lose.  At first, the leader of the pirates was full of pride because he thought he was going to win.  However, as the day passed, Jhang still had many gold pieces to throw in.  After the pirate threw in his last piece of gold, Jhang still had piles of gold pieces on the shore.  The pirate had to accept his own defeat.  He sailed away and never returned.

          Do you know how Jhang won?  You see, all his gold were pieces of basalt that he had picked from the shore.  Basalt glitters in sunlight and looks just like gold.  That’s how Jhang escaped. 

III.  Introduction to the Geography of Penghu

1.  Geographical Location

    The sea around the Penghu Islands is stormy, but the inner sea is calm as a lake.  The islands were formed from basalt, a kind of volcanic rock. Nearly one hundred rocky reefs are scattered over an area of about 60 km from the north to the south and about 40 km from the east to the west on the sea.  The islands are situated at 23°47' to 23°9' north and 119°18' to 119°42' east. 

    They are located slightly to the south of the center of the Taiwan Strait. The shortest distance to Jiayi(嘉義) in Taiwan is 24 nautical miles, while the shortest distance to Fujian(福建) in China is 75 nautical miles. The islands have an important geographical position, being the natural boundary between the East China Sea and the South China Sea.

2.  Area and Population

    The total area of Penghu is 127 sq km.  Among the islands, the island of Penghu is the largest (64 sq km), followed by Siyu (西嶼)and Baisha(白沙).  The population was highest in 1969 with over 120,000 people.  Thereafter, with people moving away, the population slowly dropped.  In September 2006, the population was about 92,000.

3. Climate and Tides

             a. Climate

          The islands of Penghu are all quite flat with little change in altitude.  There are no mountains or rivers. The three main features of the climate are the mild weather, low rainfall and strong monsoon winds.

             b.Tides

          On the islands, there is a difference of 3 km in sea level between high tide and low tide.  The intertidal zone which results from the difference in sea level between high and low tides is about 30% of the area of the islands.  This has led to the formation of unique coastal wetlands.

4.  Formation of Basalt Columns

          Basalt, the volcanic rock from which the islands were formed, probably flowed out from the centre of the earth through cracks in the earth’s surface about 18 million to 8 millions years ago. As it cooled down, the molten rock cracked into five- or six-sided pillar-like columns.  The columns were ranged according to where the molten rock flowed out.  When the molten rock cooled down, cracks perpendicular to the earth’s surface were formed.

          The basalt columns of Penghu were formed in several eruptions.  There is a lot of variety in the shapes and sizes of the columns.  The color, texture and scale of the basalt columns make them unique in all of Taiwan; these columns also rare in the world.  For this reason, the Council for Cultural Affairs nominated them as a potential “World Heritage Site.”

　

5. Geological Characteristics

             There are three special geological features in the Penghu Islands:

1. Mesas formed from volcanic rock.

2. The land slopes from the south to the north – it is higher in the south than in the north.

3. A rugged coastline. 

          The coastline is 320 km long (it is 120 times than that of Taiwan per unit area), making it the longest in all of Taiwan.  There are three types of shorelines:

1. Sea cliffs or cliffs formed from broken stones.

2. Eroded promontories or shorelines with coral reefs near the edges.

3. Sandy beaches or pebble beaches.

6. Geological Structure

          There are three kinds of common geological formations in Penghu; these are fissures, folds and faults.  Here is a brief introduction of these landforms.

1. Fissure – A fissure is formed when molten rock cools and contracts.  The tension caused by the contraction causes the rock to crack into many-sided columns.  This kind of land formation is known as a “fissure.”  Fissures are usually straight and even, but they can also be curved or they can lean in different directions.  The fissures in Penghu are its most special feature. When the fissures in the columnar basalt are horizontal, they are called crevices.

2. Folds -- When rock layers become bent or wrinkled as a result of compression, folds are formed. When the rock layers are pushed up after folding they are called arches.  If the rock layer is curved downward, it is called a syncline. In Penghu, folds are seen in Chimei, at the eroded promontory of Longcheng (龍埕) and at the sea cliff at Nioumuping (牛母坪）.

3. Faults – When rock layers crack as a result of pressure and the bodies of rock on the two sides of the crack slide past each other, faults are formed.  In Penghu, a large scale fault is seen in Chimei (七美)on the east side of Longcheng (龍埕).

7.  Water in Penghu

          There are no high mountains in the Penghu Islands that can block the moisture on land; in addition, the annual rainfall is low and the rate of evaporation is high.  There is also little surface water.  For this reason, there is not enough water resource.  To prevent the water from flowing into the sea as soon as they reach the ground, reservoirs have been built close to where the water runs out to the sea; e.g. Chenggong (成功)Reservoir,  Singren(興仁) Reservoir and Dongwei(東衛) Reservoir.
        In recent years, to prevent over-evaporation, underground reservoirs have been built to conserve water; e.g. Baisha(白沙) Chihkan (赤崁)Underground Reservoir.