Difference between revisions of "Glen Canyon Natural History"

(ok, it's late, i see how the hawk photo fits now...)
 
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''Photo: Chris Carlsson''
 
''Photo: Chris Carlsson''
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[[Image:Glen-Canyon-before-trees wnp14.jpg]]
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'''Glen Canyon at turn of 20th century, before trees planting.'''
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''Photo: [http://www.opensfhistory.org Western Neighborhoods Project/OpenSFHistory.org]''
  
 
[[Image:Islais-creek-near-source-in-glen-canyon7143.jpg]]
 
[[Image:Islais-creek-near-source-in-glen-canyon7143.jpg]]
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''Photo: Chris Carlsson''
 
''Photo: Chris Carlsson''
  
Glen Canyon's varied topography and diverse habitats make it one of the most interesting natural areas left in San Francisco. The cliffs carved above bear witness to the active seismic activity in the ancient past. Along O'Shaughnessy Boulevard the dark-red outcrops of Franciscan radiolarian chert, deposited long ago in perfectly flat beds on an ocean floor, have been warped over time into folded chevrons. Bluff lettuce (''Dudleya farinosa''), stonecrop (''Sedum spathulifolium'') and other denizens of rocky outcrops grip the cliff face. A gnarled chinquapin (''Chrysolepis chrysophylla''), the only one in San Francisco, clutches a windswept rock. In a patch of brush high above the road, the common scarlet columbine (''Aquilegia formosa'') was just barely hanging on, down to just these couple of individuals in the entire county. With help from the park's volunteer stewards, it now flourishes along the north fork of Islais Creek in the canyon below. Before entering a culvert near the Recreation Center, [[Islais Creek 1918|Islais Creek]] runs unhindered through willow woodlands and planted eucalyptus trees. It thereby joins [[Water in the Presidio|Lobos Creek]] as the only other above-ground creek in San Francisco.
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[[Image:Islais-Creek 20160911 181526.jpg]]
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'''Islais Creek flowing in mid-canyon during late summer 2016 in a very dry period.'''
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''Photo: Chris Carlsson''
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Glen Canyon's varied topography and diverse habitats make it one of the most interesting natural areas left in San Francisco. The cliffs carved above bear witness to the active seismic activity in the ancient past. Along O'Shaughnessy Boulevard the dark-red outcrops of Franciscan radiolarian chert, deposited long ago in perfectly flat beds on an ocean floor, have been warped over time into folded chevrons. Bluff lettuce (''Dudleya farinosa''), stonecrop (''Sedum spathulifolium'') and other denizens of rocky outcrops grip the cliff face. A gnarled chinquapin (''Chrysolepis chrysophylla''), the only one in San Francisco, clutches a windswept rock. In a patch of brush high above the road, the common scarlet columbine (''Aquilegia formosa'') was just barely hanging on, down to just these couple of individuals in the entire county. With help from the park's volunteer stewards, it now flourishes along the north fork of Islais Creek in the canyon below. Before entering a culvert near the Recreation Center, [[Islais Creek Remembered|Islais Creek]] runs unhindered through willow woodlands and planted eucalyptus trees. It thereby joins [[Water in the Presidio|Lobos Creek]] as the only other above-ground creek in San Francisco.
  
 
'''The diverse habitats in the canyon make it particularly important for wildlife.'''  
 
'''The diverse habitats in the canyon make it particularly important for wildlife.'''  
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The Friends of Glen Canyon Park is particularly active in providing stewardship to the canyons wildlands. Its members are occasionally seen in the canyon with spotting scopes trained on the red-tailed hawk nests in the eucalyptus trees above. They often know to the day when the years chicks fledged!
 
The Friends of Glen Canyon Park is particularly active in providing stewardship to the canyons wildlands. Its members are occasionally seen in the canyon with spotting scopes trained on the red-tailed hawk nests in the eucalyptus trees above. They often know to the day when the years chicks fledged!
  
[[Image:Habitat-tour-button.jpg]] [["Nature" and "Culture" at the Presidio |--> Habitat/Species Tour continues]]
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[[Image:Elise Beneke Tietz with cow in Glen Canyon c1909 AAD-2705.jpg]]
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'''Elise Beneke Tietz with a cow in Glen Canyon, c. 1909.'''
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''Photo: San Francisco History Center, San Francisco Public Library''
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<hr>
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[[Image:Tours-habitat.gif|link=McLaren Park]]  [[McLaren Park | Continue Habitat/Species Tour]]
  
[[Glen Canyon Park | Prev. Document]]  [[Glen Park: SF's 'Little Switzerland' |  Next Document]]
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[[Giant Powder Company | Prev. Document]]  [[Glen Park: SF's 'Little Switzerland' |  Next Document]]
  
  
[[Category:Glen Park]] [[Category:Glen Canyon]] [[category:habitat]] [[category:parks]] [[category:species]] [[category:water]]
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[[Category:Glen Park]] [[Category:Glen Canyon]] [[category:habitat]] [[category:parks]] [[category:species]] [[category:water]] [[category:1900s]] [[category:2000s]]

Latest revision as of 18:37, 5 May 2020

Historical Essay

by Pete Holloran

Glenpark$glen-canyon-rocks.jpg

Glen Canyon rocks

Photo: Chris Carlsson

Glen-Canyon-before-trees wnp14.jpg

Glen Canyon at turn of 20th century, before trees planting.

Photo: Western Neighborhoods Project/OpenSFHistory.org

Islais-creek-near-source-in-glen-canyon7143.jpg

Islais Creek near its source at the top of Glen Canyon, 2006.

Photo: Chris Carlsson

Islais-Creek 20160911 181526.jpg

Islais Creek flowing in mid-canyon during late summer 2016 in a very dry period.

Photo: Chris Carlsson

Glen Canyon's varied topography and diverse habitats make it one of the most interesting natural areas left in San Francisco. The cliffs carved above bear witness to the active seismic activity in the ancient past. Along O'Shaughnessy Boulevard the dark-red outcrops of Franciscan radiolarian chert, deposited long ago in perfectly flat beds on an ocean floor, have been warped over time into folded chevrons. Bluff lettuce (Dudleya farinosa), stonecrop (Sedum spathulifolium) and other denizens of rocky outcrops grip the cliff face. A gnarled chinquapin (Chrysolepis chrysophylla), the only one in San Francisco, clutches a windswept rock. In a patch of brush high above the road, the common scarlet columbine (Aquilegia formosa) was just barely hanging on, down to just these couple of individuals in the entire county. With help from the park's volunteer stewards, it now flourishes along the north fork of Islais Creek in the canyon below. Before entering a culvert near the Recreation Center, Islais Creek runs unhindered through willow woodlands and planted eucalyptus trees. It thereby joins Lobos Creek as the only other above-ground creek in San Francisco.

The diverse habitats in the canyon make it particularly important for wildlife.

Ecology1$native-plants$damselfly itm$forktail-damselfly.jpg

The San Francisco forktail damselfly (Ischnura gemina) is a rare species that nevertheless finds its habitat in the most unlikely places.

Photo: Margo Bors

In Glen Canyon, the San Francisco forktail damselfly is largely restricted to a drainage ditch on the northern slope. It has gone extinct at least once in the canyon, but graduate students from San Francisco State University reintroduced it from nearby populations on San Bruno Mountain.

Sf-eagle-eating-pigeon.jpg

Thanksgiving Bird!: This young red-tailed hawk is munching a pigeon right outside the window of an apartment at 19th and Dolores, on Thanksgiving Day, 2003.

Photo: Tristan Savatier

The Friends of Glen Canyon Park is particularly active in providing stewardship to the canyons wildlands. Its members are occasionally seen in the canyon with spotting scopes trained on the red-tailed hawk nests in the eucalyptus trees above. They often know to the day when the years chicks fledged!

Elise Beneke Tietz with cow in Glen Canyon c1909 AAD-2705.jpg

Elise Beneke Tietz with a cow in Glen Canyon, c. 1909.

Photo: San Francisco History Center, San Francisco Public Library


Tours-habitat.gif Continue Habitat/Species Tour

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