The Lower Cantwell Formation
The Lower Cantwell dates back to approximately 65 million years ago. An exact date has not yet been calculated. While we were in Denali, we hiked to an exposed area of the formation to observe geologic features.
This is the first dinosaur trace fossil found in Denali National Park. It is a dinosaur footprint. It was discovered by an educational group visiting the park (similar to the ASRA program). This fossil opened more opportunities to search for and study other dinosaur fossils in the park. Above is another trace fossil, most likely of a burrow created by a small animal. Wood fossil Coniferous leaves
The above picture shows layers of sedimentary rocks that have been uplifted and tilted. The large rock formation in the middle is magma (dike) that intruded the layers of sedimentary rock.
Water is heated in the Earth by magma. Super-heated water carries a large amount of dissolved minerals. The water travels through cracks in rocks and cools, leaving behind mineral deposits.
Glaciers shaped many geologic features in Denali National Park.
U and V shaped Valleys:
Slumps and Landslides
U shaped valleys were carved by glaciers traveling between the mountains and plowing away rocky outcrops, as opposed to V shaped valleys, carved by streams.
Erratics and Kettle Lakes:
The small lakes on the left of the above photo are called kettle lakes. They were formed by calved blocks of ice. As the climate warmed and the ice melted, the water left behind filled in the indentations made by the falling ice, creating kettle lakes. The rock on the right is called an erratic, it was carried from upstream by a moving glacier and left behind when the glacier retreated.
Slumps occur when the side of a mountain collapses and slides down its slope. This slump caused a river to be blocked off and resulted in the formation of Bird Lake. These slumps are usual occurrences in Denali.
Pillow basalts are formed when lava cools under seawater, forming an inverted teardrop shaped pocket as the outer shell cools faster than the interior of the flow.