EarthWatch: Vietnam’s Hạ Long and Bai Tu Long Bays

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Vietnam’s Hạ Long Bay and Bai Tu Long Bay have submerged landforms known as karsts. 

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory:  
  • NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey 
  • Image of the Day story by Kasha Patel:    
  • Adaptation to ViewSpace by Claire Blome, Margaret W. Carruthers, and Dani Player
  • Music from Music for Nonprofits 

Text, Earth Watch. Exploring the blue planet by satellite.  An image of earth from space, a mottled white snowy land mass.
Text, Vietnam's Ha Long and Bai Tu Long Bays. Sparse green islands in mottled aquamarine water. Text, Vietnam's Ha Long Bay and Bai Tu Long Bay lie along the country's northeast coast near the Chinese border. Ha Long Bay includes about 1,600 islands and islets, most topped with rainforests.
Bai Tu Long Bay, which is also a national park, spans both land and water and includes rainforests and coral reefs.
Much of the bay is a drowned karst landscape that contains impressive limestone formations, including giant pillars with conical peaks, arches, and caves.
Karst forms when rain and groundwater, which are slightly acidic, slowly dissolve limestone.
While the limestone in this region began forming roughly 340 million years ago, the karst features developed over the past 20 million years.
The bay itself is about 8,000 years old.
Zooming in on small scattered green islets in the blue water. Text, Ha Long Bay was declared a World Heritage Site in 2009 in part for its pristine examples of geoclimactic history and underwater karsts. A circle appears on the map and an arrow pointing to a small green dot, drowned karst. To learn more, go to earth observatory dot nasa dot gov.