Questions to be answered
1. Look at Blodgett Canyon (West). What shape is this large valley? What caused this valley to be created?
2. Estimate how high the Northern wall of this canyon is? What is the width of the canyon mouth?
3. Can a U-shaped valley become a V-shaped valley? Can a V-shaped valley become a U-shaped valley? Explain your answers.
4. MANDATORY: Post a picture of yourself, your signature item or GPS at GZ with the Sapphire mountains in the background. (Look East)
Message me your answers, don't post them in your log.
Blodgett Canyon is renowned as a premier, "underrated" Big Sky Country destination known for world-class big wall rock climbing, dramatic, steep cliffs and scenic hiking trails. It is often referred to as Montana's "Grand Canyon," it offers impressive, less crowded vistas and access to a rugged wilderness area.
Valley Shapes
V-shaped Valleys
V-shaped canyons are deep, steep-walled valleys formed primary by rapid downward erosion from fast-growing rivers and streams cutting through resistance rock. Often found in the youthful stage of river development, these valleys feature converging sides shaped by hydraulic action and weathering.
Key Aspects of V-shaped Canyon Formation:
- Vertical Erosion: Fast-growing flowing water erodes the riverbed faster than the sides, leading to downward cutting.
- River Youthfulness: These canyons typically form in mountains or highland areas where streams have high velocity.
- Resistant Rock: The river cuts through hard rock that resists erosion, maintaining steep walls.
- Weathering: In addition to water erosion, processes like frost wedging, break down the valley sides.
U-shaped Valleys
U-shaped canyons or glacial troughs, are primarily formed by the massive derisive power of glaciers widening and deepening pre-existing V-shaped river valleys. As glaciers flow downslope, they scour the valley floor and sides, smoothing them into steep, vertical walls and broad flat bottom.
Key Aspects of U-shaped Valley Formation:
- Glacial Erosion/Scouring: Unlike water, which erodes only at the base, glaciers fill the entire valley, eroding both sides and the bottom simultaneously.
- Modification of V-shapes: Glaciers commonly follow existing V-shaped (carved by rivers) and transform them into U-shapes.
- Freeze-thaw Weathering: Ice and snow enter rock cracks, freezing and expanding to break apart the rock, which the glacier then transports.
- Glacial Deposits: As glaciers retreat, they leave behind debris, often forming moraines - a mass of rock and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremely.
Formation of a U-shaped valley happens over geologic time, meaning not during humans lifespan. It can take anywhere between 10,000 and 100,000 years for a V-shaped valley to be carved into a U-shaped valley. These valleys can be several thousand feet deep and tens of miles long. Glaciers will spread out evenly in open areas, but tend to carve deep into the ground when confined to a valley. Ice thickness is a major contributing factor to valley depth and carving rates. As a glacier moves downhill through a valley, usually with a stream running through it, the shape of the valley is transformed. As the ice melts and retreats, the valley is left with very steep sides and a wide, flat floor. This parabolic shape is caused by glacial erosion removing the contact surface with greatest resistance to flow, and resulting section minimises friction.
