Geological Wonders
Taiwan’s geology produces landscapes that would be remarkable anywhere but are extraordinary when concentrated in such a small area. These natural wonders aren’t merely scenic; they’re textbooks in stone, illustrating geological processes and Earth history.
Taroko Gorge
Taroko Gorge is Taiwan’s geological masterpiece. The Liwu River has incised a canyon through metamorphic rock, primarily marble, creating vertical walls that in places tower 500 to 1,000 metres above the river. The marble here began as limestone, calcium carbonate sediments formed from ancient marine organisms, deposited on an ocean floor millions of years ago. As the tectonic plates collided, these sediments were buried deep within the Earth where high temperatures and pressures metamorphosed the limestone into marble.
The gorge’s exceptional depth and nearly vertical walls are possible because marble, despite being relatively soft for a metamorphic rock, is strong enough to maintain vertical faces when unweathered. The white and grey banding in the marble represents variations in the original limestone composition and the subsequent metamorphic history.
What makes Taroko particularly instructive is that you can observe active geological processes. The river continues to incise as the land uplifts. Fresh rockfalls demonstrate that erosion is ongoing. The narrowest sections—where you can nearly touch both walls simultaneously—show how the river has cut downward faster than lateral erosion has widened the canyon, a characteristic of a rapidly uplifting landscape.
Yehliu Geopark
Yehliu, on the northern coast, showcases differential erosion in sedimentary rock. The “queen’s head” and other mushroom-shaped rock formations formed because the sandstone here contains harder, more resistant layers interbedded with softer layers. As waves and rain erode the rock, the softer layers wear away faster, undercutting the harder layers and creating the characteristic top-heavy shapes.
These formations are temporary in geological terms. The “queen’s head” has a progressively thinning neck as erosion continues. Eventually, it will collapse, but new formations are constantly being created as erosion works on fresh rock. This transience makes Yehliu a lesson in geological impermanence: the landscape you see today is just one frame in an ongoing process.
The site also displays other erosion features: potholes worn by stones swirled by water, honeycomb weathering where salt crystallisation has etched patterns into the rock surface, and sea caves where waves have exploited weaknesses in the rock structure.
Penghu Basalt Columns
Penghu is built from basaltic lava flows, and its coastline displays some of the world’s finest examples of columnar jointing. These hexagonal columns formed as lava flows cooled and contracted. As the rock solidified and cooled, it developed a network of cooling cracks that propagated downward from the surface. The most efficient pattern for releasing stress in a uniformly cooling sheet of material is a hexagonal array, which is why the columns have this distinctive geometry.
The columns at sites like Daguoye illustrate this process perfectly. The vertical columns indicate that the lava flow cooled from a horizontal surface: the columns always form perpendicular to the cooling surface. The regularity of the columns indicates slow, even cooling. Rapid cooling would produce irregular, smaller-scale fracture patterns.
Penghu’s geology also tells a volcanic history. Multiple lava flows, each forming its own colonnade, stacked atop one another reveal repeated volcanic episodes. The weathering of basalt produces iron-rich, reddish soils, and the presence of volcanic bombs, large fragments of lava ejected during explosive eruptions, indicates that some volcanic activity was violently eruptive rather than the gentle lava outpouring that produced the columns.
Moon World Badlands
The “moon world” badlands of southwestern Taiwan, particularly around Kaohsiung and Tainan, present an alien landscape of deeply eroded mudstone hills. These badlands form in mudstone and shale formations that are soft, fine-grained, and impermeable to water.
The distinctive topography results from several factors. First, the rock is easily eroded: rainfall quickly incises channels into the soft mudstone. Second, because the rock is impermeable, water runs off the surface rather than soaking in, increasing erosive power. Third, the area experiences both heavy monsoon rains (which cause intense erosion) and dry periods (during which the mudstone hardens and cracks).
The result is a landscape of sharp ridges and deep gullies almost entirely devoid of vegetation. The barren grey slopes, carved into intricate patterns by water erosion, inspired the “moon world” nickname. These badlands are dynamic, as they look noticeably different after major rain events, and demonstrate how geological substrate (in this case, soft mudstone) controls landscape development.
The mudstones here are marine sediments from the Pliocene epoch (approximately 2 to 5 million years ago), and fossils of marine organisms can be found within them, evidence of their seafloor origin.
Qingshui Cliffs
The Qingshui Cliffs on the east coast are among Taiwan’s most photographed geological features. These sea cliffs rise abruptly from the Pacific Ocean to heights exceeding 800 metres, forming a nearly vertical wall of metamorphic rock.
These cliffs are steep because the rock is hard (primarily schist and marble) and because the coast is being actively uplifted. As the land rises, wave action undercuts the cliff base, causing collapse of unsupported rock above. This process maintains the cliff’s steepness even as it retreats landward.
The cliffs demonstrate several geological concepts. The presence of marble and schist indicates high-grade metamorphism: these rocks experienced intense heat and pressure deep within the Earth’s crust. The folded and contorted layering visible in the cliff face reveals the intense deformation these rocks endured during mountain building. The fresh, unvegetated cliff faces indicate active erosion and rockfall.
The Qingshui Cliffs are also a lesson in geological hazards. The section of the Suhua Highway that runs beneath these cliffs is notorious for rockfalls, demonstrating how dramatic geology creates real risks for human infrastructure.
Hehuan Mountain
Hehuan Mountain, at 3,416 metres, is accessible by road and displays periglacial features—landforms created by freeze-thaw action. Whilst Taiwan lies in the subtropics, the highest peaks experience freezing temperatures, and during the last Ice Age, the climate was significantly colder.
The rounded, smoothed bedrock surfaces on Hehuan’s peaks suggest glacial polishing, though the extent of past glaciation in Taiwan remains debated. More certainly, the presence of solifluction features (where freeze-thaw action causes soil to flow slowly downslope) and patterned ground (stone polygons formed by frost action) indicate periglacial processes.
Hehuan also showcases the vegetation transition with altitude. The treeline here sits at approximately 3,000 metres, above which only alpine meadows exist. This boundary is controlled by temperature, as trees cannot survive where the growing season is too short or temperatures too low, illustrating how geology (altitude) controls ecology.
Kenting Coral Reefs
Kenting, at Taiwan’s southern tip, features both living coral reefs and uplifted fossil reefs. The uplifted reefs are particularly instructive because they preserve ancient reef environments that can now be examined on land.
These fossil reefs consist of limestone formed from coral skeletons and other marine organisms. Dating of these uplifted reefs indicates they formed during interglacial periods when sea levels were similar to or higher than today. The fact that they now sit above sea level. By dating reefs at different elevations, geologists can calculate uplift rates.
The uplifted reefs also display karst features: caves, sinkholes, and dissolved rock formations created as mildly acidic rainwater dissolved the limestone. These karst features demonstrate chemical weathering and provide habitats for specialised plants and animals.
The living reefs offshore face modern challenges, including warming waters and human impacts, but they continue to grow and represent one of Taiwan’s most biodiverse environments.