Greenleaf Peak
Encyclopedia
Greenleaf Peak is a mountain in the Cascade Range
in the U.S. state
of Washington, located on the north side of the Columbia River
near Table Mountain, in the Columbia River Gorge
. The peak lies within the Columbia River Gorge National Scenic Area near Bonneville Dam
. It is 3424 feet (1,043.6 m) in elevation. Botanist David Douglas climbed to the summit in September of 1825, making this the first recorded mountain ascent in what is now Washington state.
Just south of the summit of Greenleaf Peak there is a dramatic escarpment
called Red Bluffs, which connects Greenleaf Peak and Table Mountain. Approximately 1300 feet (396.2 m) of the Eagle Creek formation are exposed at Red Bluffs. The Red Bluffs escarpment was created by the repeated collapse of Greenleaf Peak and Table Mountain. Massive landslides have fallen from the mountains, creating a 12 to 14 sq mi (31.1 to 36.3 km2) area of debris called the Cascade Landslide Complex. The largest and most studied landslide is known as the Bonneville Slide, which created the Bridge of the Gods and Cascade Rapids The topography of the landslide complex is uneven with roughly rolling hills and abrupt slopes. The whole area is inclined south toward and beyond the Columbia River. There may have been a cinder cone
between Greenleaf Peak and Table Mountain which collapsed during the Bonneville Slide.
The propensity of the area south of Greenleaf Peak and Table Mountain to collapse in landslides is due to the Eagle Creek formation. The rocks of the formation cover approximately 30 miles (48.3 km) of the Columbia River Gorge east of Cape Horn and consist of a mixture of past landslides, volcanic mud flows and ash falls. The formation is topped with basalt
. Water can percolate through the basalt and saturate the Eagle Creek formation. In places where the formation is relatively close to the surface and inclined downslope, such as near Greenleaf Peak and Table Mountain, water saturation can cause the formation's material to slide away, carrying the overlying basalt with it.
Between Greenleaf Peak and Table Mountain, and above the Red Bluffs, lies Greenleaf Basin. The basin averages 2040 feet (621.8 m) in elevation and is covered with forested wetlands. Greenleaf Creek flows south through the basin before plunging as a waterfall over the Red Bluffs escarpment.
In the winter of 2007-2008 there was a large landslide on the south slope of Greenleaf Peak, in the state-owned Table Mountain Natural Resources Conservation Area. Some 3 to 5 acre (12,140.6 to 20,234.3 m2) of a timbered rocky cliff slid, burying approximately 30 acres (121,405.8 m²) of forest under rubble. The slide was estimated to be about 750 feet (228.6 m) wide and 0.5 mile (0.80467 km) long.
Cascade Range
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
in the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of Washington, located on the north side of the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
near Table Mountain, in the Columbia River Gorge
Columbia River Gorge
The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. Up to deep, the canyon stretches for over as the river winds westward through the Cascade Range forming the boundary between the State of Washington to the north and Oregon to the south...
. The peak lies within the Columbia River Gorge National Scenic Area near Bonneville Dam
Bonneville Dam
Bonneville Lock and Dam consists of several run-of-the-river dam structures that together complete a span of the Columbia River between the U.S. states of Oregon and Washington at River Mile 146.1. The dam is located east of Portland, Oregon, in the Columbia River Gorge. The primary functions of...
. It is 3424 feet (1,043.6 m) in elevation. Botanist David Douglas climbed to the summit in September of 1825, making this the first recorded mountain ascent in what is now Washington state.
Just south of the summit of Greenleaf Peak there is a dramatic escarpment
Escarpment
An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
called Red Bluffs, which connects Greenleaf Peak and Table Mountain. Approximately 1300 feet (396.2 m) of the Eagle Creek formation are exposed at Red Bluffs. The Red Bluffs escarpment was created by the repeated collapse of Greenleaf Peak and Table Mountain. Massive landslides have fallen from the mountains, creating a 12 to 14 sq mi (31.1 to 36.3 km2) area of debris called the Cascade Landslide Complex. The largest and most studied landslide is known as the Bonneville Slide, which created the Bridge of the Gods and Cascade Rapids The topography of the landslide complex is uneven with roughly rolling hills and abrupt slopes. The whole area is inclined south toward and beyond the Columbia River. There may have been a cinder cone
Cinder cone
According to the , Cinder Cone is the proper name of 1 cinder cone in Canada and 7 cinder cones in the United States:In Canada: Cinder Cone In the United States:...
between Greenleaf Peak and Table Mountain which collapsed during the Bonneville Slide.
The propensity of the area south of Greenleaf Peak and Table Mountain to collapse in landslides is due to the Eagle Creek formation. The rocks of the formation cover approximately 30 miles (48.3 km) of the Columbia River Gorge east of Cape Horn and consist of a mixture of past landslides, volcanic mud flows and ash falls. The formation is topped with basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
. Water can percolate through the basalt and saturate the Eagle Creek formation. In places where the formation is relatively close to the surface and inclined downslope, such as near Greenleaf Peak and Table Mountain, water saturation can cause the formation's material to slide away, carrying the overlying basalt with it.
Between Greenleaf Peak and Table Mountain, and above the Red Bluffs, lies Greenleaf Basin. The basin averages 2040 feet (621.8 m) in elevation and is covered with forested wetlands. Greenleaf Creek flows south through the basin before plunging as a waterfall over the Red Bluffs escarpment.
In the winter of 2007-2008 there was a large landslide on the south slope of Greenleaf Peak, in the state-owned Table Mountain Natural Resources Conservation Area. Some 3 to 5 acre (12,140.6 to 20,234.3 m2) of a timbered rocky cliff slid, burying approximately 30 acres (121,405.8 m²) of forest under rubble. The slide was estimated to be about 750 feet (228.6 m) wide and 0.5 mile (0.80467 km) long.