A Geologic Story EarthCache
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This is the sixth of 6 earthcaches highlighting the amazing landscape of Denali National Park and Preserve.
Welcome to Denali Geo-Ventures, a set of virtual earthcaches that highlight the amazing landscape that is Denali National Park and Preserve. These activities are offered through the Murie Science and Learning Center, a consortium of partners working with the National Park Service to support research and education efforts in Alaska’s northern parks. This set of earthcaches was created by Alaska Geographic, a non-profit organization dedicated to connecting people with our public lands.
These Denali Geo-Ventures take you behind the scenery; to investigating why the land at Denali’s entrance is so spectacular, and how it came to be. To ensure you have a positive experience and help us protect the park, please read through all of the ‘Before You Go’ information at the bottom of this page.
At this cache, all of the geologic features that you’ve explored in the previous five caches can be seen together here - pieces of geologic history making up a more complete story of Denali’s landscape. From this vista you can see a tremendous span of geologic time. You can also see evidence of the geologic processes that created wildlife habitat that Denali has become famous for. Can you find some of these features? Can you read the story of this landscape?
Being on the northside of the Hines Creek Fault you are once again standing on the ancient Yukon-Tanana Crystalline Sequence; the bedrock of Denali. To the south, through the trees you may be able to see the rocky mountain tops made up of the Cantwell Formation on the other side of the Hines Creek fault line. Also within view is evidence of more recent geologic activities. Glacial action carved out this river canyon and scoured into this hard bedrock.
There were many glacial advances in this area, but the most extensive was the Browne Glaciation, approximately 150,000 years ago. This glacier plowed northward through the mountains here, cutting between what is today known as Mount Healy to the west and Sugarloaf Mountain to the east. In doing so, the glacier created a future pathway for the Nenana River. This action created the only river that begins south of the Alaska Range and flows north through it.
The lake you are standing above, however, was not directly caused by a glacier. This lake was formed by river action or the shifting of the Nenana River’s course over time. Thinking back to what you learned about Denali’s braided rivers, can you determine what might have caused the Nenana River’s course to meander over time? Once, this lake wasn’t even here and there was simply a narrow meander in the Nenana River that was caused by the river water eroding the outside bank. Over time, the water found a weak spot and cut through the narrow neck of the meander, and created an oxbow lake.
Today, the water flowing into and out of the lake from nearby creeks is slowed by the help of one of Denali’s year-round inhabitants. Lots of plants and animals depend on this low-lying boreal forest habitat. The beavers living here have built a dam that holds in lake water. Look carefully along the banks of the lake to see if you can spot their lodge or even catch a glimpse of one swimming. In a way, the beaver is a modern-day sculptor of its environment, much like the forces that originally created this lake. If it weren’t for the ancient sculptors of the land, the glaciers that carved the channel northward through the ancient rock of these mountains, this habitat wouldn’t be here for us to experience today.
This cache, along with the other Denali Geo-Venture caches, demonstrates the forces at work shaping the landscape here in Denali. You observed the power of tectonic activity to create very distinct geologic formations, how glaciers reshaped and rearranged those rocks, and how the combined action of geology and glaciers in the past affects the ecosystems that are present today. Each cache is unique and intriguing on its own. Together, they help tell the story of Denali’s spectacular landscape. Do you know the story of the natural landscape around your home, neighborhood or state?
To Get To This Cache: Hike the Horseshoe Lake Trail to the coordinates.
To Log This Cache: On the lake below is a beaver lodge and dam that continues to shape the landscape. On what side of the lake is the beaver dam? (North, East, South or West) Email your answer to courses@alaskageographic.org. Use ‘Denali Geo-Venture - Geologic Story’ in the subject line of your email.
Before You Go Information!!!
1. All of the Denali Geo-Venture sites are located on established park trails or roads and are within the first 15 miles of the park road. There is no need to go off these durable surfaces to find your site. Help us protect the park by avoiding the trampling of the fragile subarctic plants. Also, please abide by the Leave No Trace ethics for your entire stay in Denali.
2. Denali Geo-Ventures do not involve any physical caches to be found. You will be required to look for a clue at each cache and email your answer to courses@alaskageographic.org.
3. The completion of these Denali Geo-Ventures is easiest in the summer when the Park Road is open beyond Park Headquarters. In the winter months access to some of the caches can be done on a day hike, yet may require travel through snow and challenging conditions. For information about visiting Denali and weather conditions call the Denali Visitor Information line at (907) 683-9532.
4. Summer visitors with or without personal vehicles can participate in the Denali Geo-Ventures. If visiting without your own vehicle, you may need to make use of the free Savage River Shuttle bus to reach some of the Denali Geo-Venture sites. Consult a Shuttle Bus Schedule for hours of operation.
5. As with all visitors to Denali National Park and Preserve, you are required to pay the park entrance fee at the Denali Visitor Center or the Wilderness Access Center. Entrance fees are $10 per individual or $20 per vehicle. Several park passes are available and may be used in lieu of the park entrance fee.
6. For the east-end Park Visitor Center hours of operation visit this page of the Denali National Park and Preserve website.
7. Denali is a wilderness that is home to many species of wildlife, large and small. To ensure your safety while in this wilderness please remember to Keep Wildlife Wild and review our Bear and Wildlife Safety information.
Additional Hints
(No hints available.)