Taipei began as a small pioneer settlement rooted in Mengjia and Dadaocheng along Tamsui River over 300 years ago; it evolved into a business and commerce block and expanded eastward to areas within Taipei City, and the city's neighboring regions. In the late 1980's, Taipei's cityscape was transformed by the establishment - and its subsequent prosperity - of Xinyi Business District. Taipei's development reached hilly areas in the northeast and northwest. The urban sprawl has just about spread across the bottom of the Taipei Basin, and hilly regions at low altitudes. The City, home to more than 2.6 million, is Taiwan's capital, and the country's political, economic, and cultural hub.
Taipei City is situated in the northern part of Taiwan Island, and the northeastern tip of the Taipei Basin. It borders New Taipei City on all sides. The city's easternmost point is Jiuzhuang Ward in Nangang District; westernmost point, Guandu Estuary of Guandu Ward in Beitou District; southernmost tip, Zhinan Ward in Wenshan District; northernmost tip, Hutian Ward in Beitou District.
The city covers a total area of 271.7997 square km; it is divided into 12 administrative districts. Here is a brief overview of the city's natural environment: geologically, Xindian, Taipei and Kanjiao are the 3 great faults that span the city. The city's strata is made up of sedimentary terranes and igneous rock. In addition, Taipei City’s terrains are divided roughly into 3 types of landform: Taipei Basin, the over-thrust fault ridges, and Datun Volcanoes. Taipei has a subtropical monsoon climate, with rabidly hot summers and mild winters. The city enjoys plentiful rainfall throughout the seasons, with typhoons in the summers and falls. Tamsui, Xindian and Keelung Rivers snake across the city.
According to the geologic map released by Central Geological Survey, other than Datun Volcanoes, which are made up of igneous rock, exposed terrains in Taipei City are considered primarily as the sedimentary rock type. Igneous rock is composed of andesitic lavas and tuff breccias erupted after the beginning of the Pleistocene, and it covers the sedimentary rock of the Oligocene and Miocene. The volcanoes mostly erupt along the northeasterly tectonic lines of weakness.
There is about a dozen volcanoes in the city, formed by more than 15 magmas, and mixed with many tuff breccias. Folds and fault lines traveling in the northeastern or an east-northeastern directions define Taipei's geological landscape. Stress caused by the Philippine Sea Plate in the southeast was higher than that by the Eurasian Plate in the northwest during the orogeny process, and folds began to appear; when the force exceeded the strain threshold, the accumulated potential energy was dissipated by the release of strain as the hanging wall moved up relative to the footwall, causing a reverse fault that over-thrusts in a southwestern-northeastern direction that appears in imbrication. The primary fold is the Sifenzi oblique-axe; the primary reverse faults are: Jinshan, Kanjiao, Keelung, Taipei, Bitan, and Xindian; and finally, the primary normal fault is located by Shanchiao Fault.
Taipei City’s terrains can be divided roughly into 3 types: Taipei Basin in the southwest, Datun Volcanoes in the north, and the overthrust fault ridges in the southeast. Taipei Basin is a basin area formed by fault displacement; erosion activities by Tamsui River and its tributaries contribute to the way it looks today. Taipei City sits in the northeastern region of the basin. The bottom of the basin is low and flat, and sloping northwesterly from the southeast. Tamsui, Xindian and Keelung Rivers snake on the basin. Among all three, Keelung River has the most prominent meandering river course; the geo-morphological shifts of the course over the years have also been the most noticeable. Vertical mountain range lines the northwestern edge of the basin, while valleylike ridges skirt the basin's northeastern and southeastern borders.
Datun Mountains consist of a group of 10 volcanic mountains formed by breccias and magma expelled by the volcano. Most of them are volcanic cinder cones; a minority of which are composite volcanoes. The remains of craters can still be spotted on the top of several volcanoes. Several stretches of lava terraces and a dozen depressions encircle the mountainside. Vents formed by post-volcanic activities scatter atop the Jinshan fault. The river system on Datun Volcanoes is radial; waterfalls here are formed by the protruding hard rocks. Due to the increase of drillings and data gathered from radiometric dating, expert opinions on the terrestrial evolution in Taipei or Taipei Basin have also varied.
3. RiversOther than Beihuang Creek that runs along the city's northern border, rivers in Taipei City belong largely to the Tamsui River system, which consists of Dahan River, the main tributary; and 2 other minor tributaries - Xindian and Keelung Rivers. The section where Xindian and Dahan Rivers merge is known as Tamsui River, in a narrow sense. Jingmei River is Xindian River's tributary, while Shuangxi is Keelung River's tributary.
The stretch along downstream Tamsui River - the section that is nearing sea levels - is susceptible to tidal highs and lows. The area, scope of the tidal fluctuation (tidal reach), the interaction of the river and the sea, and the effects of tidal reach are dynamically defined by the discharge of the river, the tides, and the nature of the river. Among which, the discharge of the river is most-easily affected by the tidal reach. Keelung River's tidal reach is more regular than that of Tamsui, Dahan, and Xindian Rivers. Tidal fluctuations in the headwaters and downstream areas are also more noticeable.