Sam Phan Bok
Interesting facts
- In the Isan dialect a "bok" is a natural pool or hollow in rock, which gives the reef its name.
- The potholes come in many outlines, from circles and ovals to shapes that resemble stars and hearts.
- Sam Phan Bok shot to national fame around 2009, when a Tourism Authority of Thailand campaign featured it with pop star Thongchai "Bird" McIntyre.
- The reef sits on the outer bank of a bend in the Mekong, where the river narrows and its current speeds up.
- Its rock is a pebbly sandstone, and the pebbles themselves, swirled by eddies, act as the grinders that drill the holes.
- A Chulalongkorn University study mapped the potholes by drone and sorted them into five types, including lateral, hierarchical and coalesced forms.
- Researchers found the holes form where three things meet: horizontal rock beds, a narrow fast-flowing channel and an eroding outer river bank.
Why it is worth it
Sam Phan Bok is a riverbed that rises out of the Mekong for only part of each year. When the water drops in the dry season, roughly from October to May, a broad shelf of sandstone emerges in the middle of the river on the Thai–Lao border, pitted with thousands of round holes, basins and channels. Some are shallow bowls that hold water like mirrors; others are deep, smooth-walled shafts and arches carved through the rock. Seen from above, the exposed reef looks like a miniature canyon country, which is why it has been nicknamed the "Grand Canyon of the Mekong" or of Thailand. When the monsoon floods arrive, the river rises again and the whole landscape vanishes beneath the water.
The name translates roughly as "three thousand hollows" or "three thousand shallow pools", after the countless potholes scattered across the rock. They are the work of the Mekong itself. The sandstone belongs to the Phu Phan Formation of the Khorat Group, the rock series that underlies much of the Khorat Plateau of northeastern Thailand. Over millions of years, swirling currents in the rainy-season floods have spun sand and pebbles inside cracks in the rock, grinding them out into ever wider and deeper cavities, until the shelf has become a maze of more than three thousand basins and potholes. The process continues each year as the river rises and falls.
The rock reef is the largest of its kind in the Mekong and is made up of several distinct sections, including Hat Hong, Pak Bong and Lak Sila Lek. It lies at Ban Phong Pao, in the Lao Ngam subdistrict of Pho Sai District, in Ubon Ratchathani Province — the far eastern corner of Thailand's Isan region, some 700 km from Bangkok. Across the channel lies Laos, and in the low-water months the reef stands out as a sculpted island of rock between the two banks.
Getting there
Sam Phan Bok lies in Pho Sai District on the Mekong, about 63 km from the town of Phibun Mangsahan. The nearest airport is Ubon Ratchathani Airport (UBP), about 83 km away.
On these lists
From the encyclopaedia
Sam Pan Bok also known as the "Grand Canyon of Thailand" is a seasonal attraction and the biggest rock reef in the Mekong River. Sam Phan Bok is a group of sandstone that has been eroded by streams from the Mekong River every rainy season until this area now has more than 3,000 bok with countless basins and potholes. It is located 700 km from Bangkok. Sam Phan Bok translates as '3,000 shallow lakes'. It is in northeastern Thailand (Isan), on the bank of the Mekong. Administratively, it is in Baan Phong Pao, Lao Ngam Sub-district, Pho Sai District, Ubon Ratchathani Province. The holes in the sandstone rocks had developed over millions of years. There are different sections of Sam Phan Bok including Hat Hong, Pak Bong and Lak Sila Lek.
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