OwensPeak#1

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Owens Peak #1: Geology, Lichens & Some Plants
© W.P. Armstrong, 25 May 2012

View of Owens Peak looking north from the Palomar College Arboretum.

View from Owens Peak looking southwest toward Palomar College. In the foreground is an outcrop of Santiago Peak Volcanic rock. In the distance is the new Natural Science Building and the Palomar College Arboretum.

An outcrop of Santiago Peak Volcanic rock at the summit of Owens Peak, better known as Palomar "P" Mountain. This dark, fine-grained, very hard rock dates back to the Jurassic Period, 145 million years ago, to a time when dinosaurs walked the earth. This heavy rock is resistant to erosion and forms some of the higher topography in coastal San Diego County.

An outcrop of Santiago Peak Volcanic rock at the summit of Owens Peak.

Santiago Peak Volcanic rock from the summit of Owens Peak.

Magnified view of Santiago Peak Volcanic from Owens Peak showing rectangular plagioclase crystals.

  Santiago Peak Volcanic Rock In San Dieguito River  
San Marcos Gabbro In Nearby The San Marcos Mts.
Rock Formations On The Santa Rosa Plateau
Basalt Outcrops On The Santa Rosa Plateau

Jerusalem cricket (Stenopelmatus) on Owens Peak (Santiago Peak Metavolcanic).

Lichens On Owens Peak

An outcrop of Santiago Peak Volcanic rock at the summit of Owens Peak, better known as Palomar "P" Mountain. This dark, fine-grained rock with white flecks dates back to the Jurassic Period, 145 million years ago. The lemon-yellow, crustose lichen is Acarospora socialis with a small patch of A. bullata (far right). The Acarospora doesn't have the marginally lobate thallus of Pleopsidium flavum and P. chlorophanum. The brown crostose lichen A. bullata is similar to the common species A. fuscata.

  List Of Lichen Images On Wayne's Word  

An outcrop of smooth, white-flecked Santiago Peak Volcanic rock at the summit of Owens Peak. The foliose lichen is Xanthoparmelia cumberlandia.

The weathered surface of this Santiago Peak Volcanic rock outcrop at the summit of Owens Peak is covered by colonies of crustose lichen. The circular gray colonies are Dimelaena radiata.

I originally identified this yellow crustose, areolate lichen as Acarospora schleicheri because it lacked the bright chartreuse coloration and marginal lobation of Pleopsidium flavum and P. chlorophanum. However, most modern lichen floras state that A. schleicheri is a soil (terricolous) species. In fact, even A. H. Magnusson (1929) describes A. schleicheri as a soil lichen in "The Yellow Species of Acarospora in North America" (Mycologia 21 (5): 249-260). In the latter reference under "growing on stone" this yellow lichen keys out to A. socialis. According to Kerry Knudson (personal communication, 2007), A. socialis is indeed the correct name for this species. The brown crustose lichen was identified by Charis Bratt as A. bullata. The white crustose lichen with marginal lobation is Dimelaena radiata.

Yellow coblestone lichen (Acarospora socialis) on Owens Peak. The areoles are about 1-1.5 mm in diameter, some of which contain a sunken hymenial layer. Photographed with Nikon D-40x with manual 55 mm micro-Nikkor macro lens and 3 extension rings at f-22 (one second exposure).

Tardigrades Belong To The Seldom-Seen Phylum Tardigrada

Magnified view of yellow coblestone lichen (Acarospora socialis) and tardigrade (black arrow) on Owens Peak. The areoles are about 1-1.5 mm in diameter, some of which contain a sunken hymenial layer. The tardigrade is only about 0.25 mm long (1/100 of an inch).

Minute tardigrades (Phylum Tardigrada) are only about 0.25 mm long (1/100 of an inch). Although they are fairly common on mosses and lichens, they are rarely seen. They are called "water bears" because of their fat body with stubby legs bearing claws at the tips.

Numerous gray colonies of Dimelaena radiata.

The bright orange crustose lichen (Caloplaca) occurs sparingly in Owens Peak.

Tasty Salad Plant On Owens Peak

Miner's lettuce (Claytonia perfoliata ssp. perfoliata) is abundant on shady, north-facing slopes in early spring.

A delicious miner's lettuce-avocado salad for dinner.

Be Very Careful When Reaching Into A Patch Of Miner's Lettuce!

Southern Pacific rattlesnake (Crotalus viridis ssp. helleri).

  Unobstructed View Of A Southern Pacific Rattlesnake  

Interesting Spiders On Owens Peak

Orb weaver spider (genus Metepeira): The web consists of both an orb web and an irregular 3-dimensional web. The retreat is a tangled, knotted web made with debris and leaves woven into the silk, placed so as to make a small protective tent for the spider. When disturbed it quickly drops out of the leaf cluster retreat and returns when the danger has passed. The genus was identified by Jim Berrian of the San Diego Natural History Museum.

Silver argiope (Argiope argentata) on Owens Peak (28 October 2010).

  See Banded Argiope On Owens Peak  
See A Tarantula on Owens Peak

Some Plants On Owens Peak

Venus looking-glass (Triodanis biflora), a seldom-seen wildflower in bellflower family (Campanulaceae).

A few boneseed shrubs (Chrysanthemoides monilifera ssp. monilifera) are naturalized on shady, north-facing slopes.

  More Images of Boneseed (Chrysanthemoides monilifera ssp. monilifera)  

Petrorhagia dubia (Carophyllaceae), an uncommon naturalized weed on Owens Peak.

Mission manzanita (Xylococcus bicolor).

Wild sweet pea (Lathyrus vestitus var. alefeldii)

California poppies (Eschscholzia californica).)

Telegraph weed (Heterotheca grandiflora) is now considered to be a native plant.