Glacier National Park: Stromatolites

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Home to fossilized algae mounds known as stromatolites, Glacier National Park provides tourists and paleontologists alike the opportunity to view these ancient geological formations found in certain park areas. Read More

  • Stromatolites are ancient fossils of blue-green algae mounds dating more than 1.5 billion years in age.
  • These fossilized bacterial mats can be viewed at high elevations, mainly in Glacier Park’s east side.
  • Take a hike near Logan Pass, Grinnell Glacier, or Swiftcurrent Glacier, and see if you can spot these geological features.


Glacier’s stromatolites date from the Precambrian era - some 1.5 billion years ago - when layers of blue-green algae formed bacterial mats in the warm, shallow sea bottoms that covered what is now Glacier National Park. Sometimes referred to as “sliced cabbage” due to their concentric ring formations, these algae mounds were responsible for providing earth with much of its oxygen rich environment, through the process of photosynthesis; at the time, carbon dioxide dominated the atmosphere. Today, paleontologists from around the globe travel to Glacier Park to study the stromatolites. Living colonies can still be found in reefs around the Bahamas and Australia.


Stromatolites are mainly located at high elevations, in the east side of the park. The Altyn and Siyeh Formations provide excellent examples of these historic geoligical records. Productive viewing areas are along the east side of Going To The Sun Road, on Logan Pass, and near Grinnell Glacier. Stop in at a ranger station for more information and locations.


Summer is the best time to view stromatolites as snow cover will be absent or minimal. Due to their location at high elevations, access will often be contingent upon Going To The Sun Road accessibility and trail conditions.


Hiking: To view stromatolites, visitors must often incorporate a hike as part of their excursion. Take the popular hike to Grinnell Glacier, keeping your eye out for these fossils:

  • Trailhead: Grinnell Glacier Trailhead
  • Trailhead Location: Near Many Glacier Hotel
  • Distance: 6 miles (one-way)
  • Ascent: 1600 feet
  • Difficulty: Easy - Moderate

Photography: Stromatolites might well be one of the oldest structures you ever record on camera!