Geographic locationPenghu locates on the Taiwan Strait between China and Taiwan in Asia. It is the only island county of Taiwan. When the time of low tide comes, more than one hundred isles appear. Therefore, the number of the total isles varies. At a rising tide, there are, generally speaking, 90 isles scattered between north latitude 23o12’;to 23o 47’ and east longitude 119o19’ to 119o43’. The utmost east isle is called "Zhamu isle" , the utmost west isle is called "Hua isle", the utmost south isle is called "Cimei isle", and the utmost north isle is called "Dogiao isle". The utmost west isle is also the utmost west boundary of Taiwan. Another unusal thing about Penghu isles is that the tropic of cancer goes through the "Hoojing isle" , one of the 90 isles.
Penghu locates on the Taiwan Strait between China and Taiwan in asia. It is the only island county of Taiwan. When the time of low tide comes, more than one hundred isles appear. Therefore, the number of the total isles varies. At a rising tide, there are, generally speaking, 90 isles scattered between north latitude 23o12’to 23o 47’ and east longitude 119o19’ to 119o43’. The utmost east isle is called "Zhamu isle" , the utmost west isle is called "Hua isle", the utmost south isle is called "Cimei isle", and the utmost north isle is called "Dogiao isle". The utmost west isle is also the utmost west boundary of Taiwan. Another unusal thing about Penghu isles is that the tropic of cancer goes through the "Hoojing isle" , one of the 90 isles.
Measure of the area
The Penghu archipelagoes scatter all over the ocean and extending around 60km north to south, 40km west to east. The total measure of the area of the 90 isles is around 127.9636 square kilometers. 19 isles are populated and the total measure of the area is 124.9392 square kilometers. 71 isles are inhabited with no one and the total measure of the area is 3.0244 square kilometers. The biggest isle is "magong isle" and another 4 big isles by order are yuweng isle, baisha isle, cimei isle and wang-an isle
LandformsThe coastline of penghu is crooked and lasts for 448,974 long. Except for the common cape bays, we can also see wave-erosion platform, wave-erosion cliff, wave-erosion cavity, sandy coast and rocky coast landforms along the coast area.
The lay of the isles are mostly gentle and almost every isle are surrounded by cliffs. The top is flat and no obvious ups and downs of the high mountains can be felt. It is a typical square mountain landform. The main reason to cause this landform is that the volcanos under the ocean have erupted with basalt flow. This flow came out with many layers of water-made rock formations of marine facies fossil. After many times of slow activities under the sea, a more flat under-ocean landform occurred. with a few more times of the change of the sea level, the landform is exposed in the air and has been eroded into what it looks like today and also becomes the most obvious landmark of penghu.
The lay of the lands slightly slides from south to north and the highest point is at 70m on "damao isle". Then going toward north by order comes 64m on isle cimei, 54m on wang-an, 56m on magong, 24m on baisha, 18m on jibei and 14m on mudou. It get’s gentter going north to the Da-yao reef, and Er-yao reef...etc.
The soil formation in penghu is mainly influenced by climate and geology distribution. Soil distribution and category is quite simple, too. Its soil is mostly formed by basalt and coral reef. Different coasts are influenced by different tides and sea winds and therefore form different kinds of soil. Generally, we divide them into two categories: the ancient geology layer soil, and the basalt geology layer soil. The former is mainly formed by feldspar with sodium held; and secondly formed by mica, amphibole, and augite; and is neutral plus acidity soil. The latter is mainly formed by basalt, calcium feldspar and augite. It belongs to neutral plus basicity soil.
Penghu is located at the edge of the Asian continent and its climate is deeply influenced by the large area climate. Penghu is roughly located on the tropical of cancer. Its average temperature of the year is 23°c ; the lowest is 16.2°c in February and the highest is 28.3°c in July. Surrounded by the ocean, the temperature in penghu is logically moderate. But due to the lack of vegetation on the ground, penghu is heated by the sunshine in summer and becomes hot even with the south wind swaying. In winter, with the strong northeast trades blowing, people feel colder than it really is.
Due to the flat terrain and lack of high mountains, an orographic rain is impossible to occur. And the average annual rainfall is only 1000mm. Plus factors such as wind velocity, sunshine..., the annual amount of evaporation can reach 1600mm.
The difference between dry season and rainy season is obvious. Every October to next march is the dry season and the amount of rainfall is around 200mm; every April to September is the rainy season the the amount of rainfall is around 800mm. It rains about 95 days an year.
The rainfall in Penghu is neutral(June 1st, 1997, pH 7.69 according to the measure stand of the government). This is because this area has less air pollution, and less chemical compounds that cause acid rain. Also when the seawater evaporates into the air and forms the salt that suspends in the air and eventually is absorbed by the rainfall, it might even make the rainfall possessing basicity.
MonsoonThe strong monsoon is a special natural phenomenon in Penghu. Penghu is located in the monsoon standard area and when the northeast monsoon during autumn and winter goes through Taiwan Strait which shaped like a tunnel, its blast strengthens and often bathe Penghu in its chilly wind. Under this monsoon system, Penghu area is bathed with the wind from high latitude in winter and mostly northeast monsoon. Due to the lack of landform protection, the wind speed in Penghu is quite fast in winter and usually it is at least 6m/sec (which equals level 4) from October to next Januarary. However, when there is continental cold air mass coming toward south, the wind speed could reach level 8 and sometimes 12. Above the ocean, the wind speed
The wind velocity changes greatly in Penghu because of the ocean. Every winter from October to March, the percentage for the wind velocity to be over 10m/s is 56% and in summer is 7.5% only. And the percentage for the wind velocity to be under 5m/s is only 15% in winter and 54% in summer. This reduces winter activities in Penghu and the number of tourists. This is what we called the dull season of Penghu.
Daily change of the wind direction and wind velocity is not obvious. In other areas such as Taiwan or neighborhood ocean areas, land winds and sea winds circulate. Daytime in summer, the wind blows from ocean to land, and in the evenings, it blows from land to the ocean. But Penghu is surrounded by the ocean and with little measure of the area, therefore there is not enough gap to produce this circulation. Thus, in all winter, the northeasterly wind blows and in all summer, the southwest wind blows.
Penghu is surrounded by the ocean with clear water and both the North Shallow Fishing ground in the north and the South Shallow Fishing ground in the south. Also with the branch of the Japan current [ the Kuroshio ] passing by, it has been a great natural fishing ground since long ago. The main ocean currents are:
The China coast cold current: this coast cold current influences mostly the west side ocean area of Penghu. It is originates from the north of the Yellow Sea and flows along the east coast of Chinea toward south. With a large amount of water pouring into, this current is quite strong especially in summer with the rainfall and contains little salt. In winter, this current is strengthened by the northeaster wind and the water temperature is lower than the Japan Current. In summer, the southwest wind makes it weaker and the water temperature is similar to the Japan Current. In winter, fish swims toward south along with this current and gather up at the west side of Penghu.
The branch of the Japan Current: the main stream of the Japan Current flows toward north along the east coast of Taiwan with its branch flowing passing the Bashi Channel and entering the South China Sea to form a counter clockwise current; the other part of the branch turns to flow along the west coast of Taiwan toward north and reach the Penghu area, and then flows further to meet the Japan Current. Stopped by the northeaster wind, this current mostly flows to the South China Sea and only little part of it flows into the Penghu ocean area. With the summer southwest wind strengthening this current, it mostly flows into the Taiwan Strait and both the water temperature and the salt contained are higher than the other two ocean currents. Therefore it can bring fishes that come from tropical Pacific Ocean and the Indian Ocean in summer.
The South China Sea Monsoon Current: in winter, one branch of the Japan Current and the China coast cold flow go together into the Penmghu area and form a counter clockwise current which makes the South China Sea monsoon current influences nothing in this area. In summer, with strong southwest monsoon blowing, this current flows into Taiwan Strait and turn toward northeast. Therefore this current possesses rich rainfall and river water with it. Generally speaking, in July, the Penghu area is influenced more by the branch of the Japan Current and the South China Sea Monsoon Current. With various cold and warm currents meeting here, a large number of plankton is produced and this provides rich food for great aount of fishes.
in Penghu there is the tide called"halfday tide". Everyday, there will be two high and low tides. Generally speaking, along the coast of the both sides of the waterway, the tides flow toward north when at hightides and toward south when at lowtides. Tides have great influence on penghu. For example, the number of isles. And the intertidal zone forms an important working field for people in penghu. Also this zone is a great relax place for visitors and tourists.
according to the central Central Wetaher Bureau, from July,1981 to June, 1988, every October to next march, with the winter northeast trades blowing, the waves could be 1.7m high and 52% of waves will be higher than 1.5m. Every april to September, with the summer southwest Monsoon blowing, the waves can be 0.8m high and the percentage for waves to be lower than 1m is 72% M. Sometimes, when the wind and the waves are too strong, transportation on the sea might be interrupted.
Measure of the area
Landforms and climate in Penghu are special compared to others. For example, its surface soil layer is quite thin and therefore the function of keeping water is not very good. It is called a dry breeding environment. Except for drought, Penghu suffers from strong wind and salt disaster brought by typhoons. These disasters cause plantations to grow their leaves thicker and covered with fuzz to store water better. The number of important plants can reach more than hundreds.
Pagoda trees are the most common plant, one of them is Tong-lian pagoda. It is the county tree because of its outlook; and the county flower Gaillardia pluchella Foug is also the strong plant grown all over Penghu. Besides, with its unique biological environment, there are also many valuable plants only can be seen in Penghu such as Ipomoea imperati (Vahl.) Grisebach, Myoporum bontioides A. Gray, Scaevola hainanensis Hance, Cassia sophora L. var. Penghuana Y.C.Lin & F. F. Lu , Glycine taacina (Labill) Benth, Justicia cilata (Yamamoto) Hsieh & Huang, and Sida veronicaefolia Lam . And some of them can be made for people to drink for body health.
Earlier people in Penghu use special stones to build wind proof walls and cultivate their farmlands in beehive shape. These are characteristics of Penghu that people grow grain corns, peanuts, sweetpotatos on ordinary famrs and grow vegetables and fruits within the walls. Also they grow many kinds of important and famous cash crops.
The government plant forestation trees for wind-proof and beautification purposes. Their skills improved gradually. Also we see mangrove in Penghu which adds vitality for the coast.
The seaweed recource is rich in Penghu and is also the first in Taiwan. Among Cyanophyta, green algae, fucoid and red algae, 40 kinds of them can be found in Penghu. Some of them are of cash value and mostly they are produced in winter from December to March. Presently, they grow these crop naturally and by breeding.
From the biological geograph point of view, the coral reef biologic system around Penghu isles belongs to the Indian-Pacific system. To Penghu, The Japan Current tides stretch their bayous into Taiwan strait and become obviously one important reason why corals live well in Penghu water area. They include madrepore and many other kinds of corals.
Madrepore forms the coral reef mostly seen near the front endof the intertidal zone along coasts. some of them stretch outward for more than 10km. we can see some distribute in belt shape near the outer sea of Long-man harbor. Others can be found in the water area near east yuanbay isle, south bird isle and chimay isle. But soft coral needs cleaner water to grow, therefore, it is less seen in the Penghu water area compared to madrepore.
What is worth mentioning is that there is a coral forest made by scallop soft coral and soft coral and it is indeed a very unique undersea biological view.
Fish in this area can reach at least 145 families and 700 species according to surveys. Most of them are Perciformes of hardbone fish category. And these are the common fish species that survive in the reef rock sea area. As to the Penghu fishery resources, it is long lasting because of the rich and various grown fish supply and the rich young fish resource. Mostly, the young fish species include red sea bream, Lethrinidae, Sphyraena japonica and Fuscous spinefoot. Every May and June, people see the magnificent view of these young fish swim in big crowd.
As to the along the coast seabed rest fish category, groupers are the most common. They mainly inhabit in the reef rock area at the shallow sea. Others are Cromileptes altiveilis (also called mouse grouper ) or Leopard coralgrouper (also called?o±o). Also in this area, there are many smaller but colorful species such as labroid family, Chaetodontidae, and sparrow porgy family. Other fishery resources such as shellfish, carapace, and echinoderm are of rich reserves.
Green Turtle and dolphin
Green Turtle, which is quite seriously taken in the recent years though, is haning a decreasing population getting less and less. And Penghu is one of the areas that Green Turtle regularly go and lay eggs. Therefore, Green Turtle also becomes one of the valuable pronouns of Penghu. Another valuable animal in Penghu is dolphin. Dolphins belong to small tooth-whale category and have as many as 260 tooth. The Penghu people call them "sea pig","sea mouse" or"black russian". Their IQ can be compared to primates. Dolphins use sounds to exchange signals and contacts. From every winter to the end of next March, they swim in groups in the outer sea of Penghu. The main species include Spinner Dolphins, Gill’s Bottle-nosed Dolphins and Bottle-nosed Dolphin. Once in a while we can see smaller False Killer Whale too.
The bird resources in Penghu is so rich that people call it the paradise of birds. As the midway stop on the immigration route of east-asia migrant birds, panghu therefore is with various kinds of birds. According to a survey in 2003, birds in penghu are as many as 14 ,40 family , and 317 species. One thing unusal is that birds that are found and being recorded in penghu are 410 species, which are three-fourth of the number of Taiwan. And to analyze those records, it’s easy to find out that only one-fifth of these birds stay. Therefore, migrant birds are still the main kinds of it.
The migration of Penghu birds are the most frequent from January to april every year, and then it lessens after may. June and July are the two months with the fewest birds. But this period of time is also the most special time for the birds of scray family on isles like damow, hsiomow, jishan and dinggou. In autume like September to December, it is the second best season for birds to move and also it is the time when migrant birds are ready to go south for winter. Generally speaking, different families of birds in Penghu get to different inhabited locations. For example, the between-tide zone by the isle coast (Scolopacidae!K), reservoir area (egret, teal...), the windbreak forest or farming land (Thrushes, Fringllidae or Sylviidae!K), and depopulated isles at the Nanhai sea (Laridae!K).