Savage River EarthCache

Denali National Park is located in central Alaska and is a breathtaking wilderness gem known for its stunning landscapes and abundant wildlife. At its heart stands Denali, the highest peak in North America, majestically dominating the horizon. The park's vast expanse covers over six million acres, offering visitors the chance to explore rugged mountains, glaciers, boreal forests, and alpine tundra. Wildlife enthusiasts are drawn to Denali for its diverse fauna, including grizzly bears, moose, wolves, and caribou.

The Savage River, a captivating geological feature within Denali National Park, stands as one of the intriguing braided rivers found in the region. These distinctive watercourses exhibit a remarkable interplay of ever-changing channels that elegantly meander across wide sediment beds, creating a visually stunning and dynamic landscape. While most braided rivers in the park owe their behavior to glacial melt, the case of the Savage River unveils a unique and intriguing geological story. Unlike its glacially influenced counterparts, the Savage River's braiding phenomenon can be attributed to a combination of geological factors. The high sediment input plays a pivotal role in shaping the river's intricate network of channels. The surrounding landscape comprises brittle rocks that are highly susceptible to weathering and erosion. Over time, these rocks break down into fine particles and sediments, which are easily transported by the flowing water of the river. Adding to the intriguing mix of factors, the headwaters of the Savage River display a relative lack of vegetation. Vegetation, such as trees and shrubs, typically serves as a stabilizing force in many river systems, reducing the speed of water flow and preventing excessive erosion. However, in the absence of such stabilizing vegetation in the Savage River's headwaters, the river's flow remains relatively unconstrained. As the Savage River meanders through its course, it carries a significant load of sediment. The combination of high sediment input and the unrestricted flow leads to the deposition of these sediments in the form of sandbars, gravel bars, and islands along the riverbed. Over time, these sedimentary deposits influence the river's path and contribute to the braiding phenomenon, where the channels continually shift and divide.

About halfway between the Savage River vehicular bridge and the Savage River Loop Trail footbridge to the north, lies a geologically significant transition zone that offers insights into the area's glacial history. Upstream (south) from this point, the Savage River flows in a broad and shallow manner, carving through a U-shaped valley that bears the unmistakable signature of glacial scouring. This U-shaped valley formation is a characteristic feature of glacial erosion, where immense glaciers once moved through the landscape, shaping and widening the valley over time. In contrast, as one proceeds downstream (north), the river's flow accelerates, leading to a narrowing and deepening of the valley. The river's forceful action has created a V-shaped valley downstream, a distinctive feature associated with river erosion processes. Over the years, the Savage River has chiseled away at the surrounding bedrock, refining the V-shaped valley we observe today. When crossing the vehicular bridge, you can notice these contrasting valley shapes as they serve as a window into the region's geological past. While the canyon's topography bears traces of more extensive glaciations that occurred over two million years ago, the river's persistent flow over time has significantly contributed to the shaping and erosion of the V-shaped canyon that exists today. This juxtaposition of U-shaped and V-shaped valleys in the Savage River area offers an exciting opportunity for geologists and nature enthusiasts alike to explore the profound impacts of both glacial and river processes on the landscape.

Erosion is a natural process that transforms the Earth's surface by wearing away rocks and soil through different forces. There are several key ways this happens. First, water erosion occurs when rain or rivers move small particles of soil and rocks. Over time, this can carve valleys and shape the land. Think of it like water sculpting the earth. There is also wind erosion, which happens in dry areas where the wind can lift and carry loose dirt. This can lead to the creation of sand dunes and smooth landscapes where the wind has blown away the soil. Another type is glacial erosion. Glaciers are huge sheets of ice that move slowly, carrying rocks and dirt. As they move, they can shape mountains and even dig deep valleys, giving the land its unique look. Gravity erosion is also important. When things on steep slopes fall due to gravity, they can reshape the land. This might result in landslides or rockfalls, changing the landscape around them. Chemical erosion occurs when rainwater and chemicals break down rocks slowly, making them weaker. This can make the rocks more susceptible to other types of erosion. In colder areas, ice erosion comes into play. Water gets into cracks in rocks, and when it freezes, it expands and breaks the rocks apart. You might notice rocks with cracks that look like they've been forced open. Even plants and animals are part of the process. Plant roots can grow into cracks in rocks and break them apart. Animals that dig, like rodents, can also move soil around. All these different types of erosion work together, gradually shaping the Earth's surface.

1. Compare and contrast the sections of river located upstream and downstream from the posted coordinates. How are they similar and how do they differ?
2. Describe the differences in erosional patterns between the U-shaped and V-shaped valleys in the Savage River area. How do you think the areas past glacial history affected the erosional patterns which you see today?
3. What factors might have led to the transition from a U-shaped valley upstream to a V-shaped valley downstream? How has the Savage River's flow over time played a role in this transformation?
4. Upload a photo taken with the Savage River. You don't have to be in the photo, though it is strongly encouraged.