Southern California’s Highest Mountain

Google Earth Pro Oct., 2019 image showing location of San Gorgonio Mountain.

 San Gorgonio Mountain is the highest peak [11,503 feet (3506 m)] in southern California. The peak is 27 mi (43 km) east of the city of San Bernardino, San Bernardino County and is a easy drive from most of Los Angeles and Orange counties. It is the peak with the greatest vertical gain (5,840 feet) in California. The mountain hosts the longest recorded line of sight in the contiguous United States; it is plainly visible from the summit of Mt. Whitney, 190 miles away.

View north-northeast from a commercial airliner. Image taken in mid July, 2010.

Closer view north from the same airliner. San Gorgonio Mountain has a few patches of snow near its summit. Under the wing, Big Bear Lake is visible. The mountain has a somewhat pyramid shape with a steep north face and a slightly shallower south face. 

An even closer view of summit of San Gorgonio Mountain. The summit plateau is large and broad (1 square mile). The summit has an Alpine climate, and snow can be present, even as late as mid-July. 

Northwest view of San Gorgonio Mountain (its summit has a few patches of snow left on it). Three major southern California rivers have their source on the mountain: the Whitewater River (shown here just right of the center of image), the San Gorgonio River, and the Santa Ana River.

San Gorgonio Mountain is part of the Transverse Ranges, an east-to-west mountain chain formed by tectonic forces between the Pacific and North American plates along the San Andreas fault, which lies just south of San Gorgonio Mountain.

The mountain is a massive block of quartz monzonite igneous rock (please see my earlier post--March 3, 2017, San Andreas Fault Displacement of a Distintive Granite), which sits on an ancient platform of Precambrian gneissic metamorphic rocks. Glacial and fluvial deposits dominate the surface of the lowest part of the mountain. During the Pleistocene “Ice Age,” there were two separate episodes of glaciation (both Wisconsin age, which was 75,000 to 11,000 years ago) on San Gorgonio Mountain, as evidenced by cirques and huge terminal embankments of coarse angular debris, up to 700 feet thick.

An ancient "sundial"

The common name of the gastropod genus Architectonica Röding, 1798 is the "sundial" snail. There are140 extant (recent) species, and they have distinctive discoidal shells with a high "spiral staircase" in the center of the underneath side of the shell. Architectonica is widespread today, and most of the species live between 40°N and S, in subtropical to tropical marine waters (e.g., Indo-Pacific, East Africa, Japan, Hawaii). Although they range in depths between intertidal and abyssal, they are most commonly found in 10-65 m depths. They are carnivorous gastropods and prey mainly on sea anemones, sea pens, and corals.

Architectonica is classified as belonging to the family Architectonicidae Gray, 1850, which, in turn, belongs to a poorly resolved group of snails known as the "lower heterobranchs," whose larval shells are diagnostic in their morphology.

The following three images are of a recent shell of Architectonica perspective (Linnaeus, 1758), from Oman. The views are dorsal, apertural, and ventral, in the order they are shown. The specimen is 48 mm in diameter and 25 mm in height.

The next two images are of the fossil Architectonica cognata Gabb, 1864, of middle Eocene age (approximately 48 million years old), from southern California. The views are dorsal and ventral, in the order they are shown. 

The central region of this specimen is "plugged up" with hard siltstone. Careful cleaning is needed in order to expose the delicate shell underneath. Cleaning of fossil specimens demands expertise, otherwise, critical features can be damaged.

The geologic range of Architectonica is Paleocene to Recent. Architectonicids do not occur in older rocks (Mesozoic and Paleozoic).

For those who seek more detailed information (i.e., I used this reference for many of the above facts), see:

Bieler, R., and R.E. Petit. 2005. Catalogue of Recent and fossil taxa of family Architectonicidae Gray, 1850 (Mollusca: Gastropoda). Zootaxa 1101:119 pp.

MASTODON VS. MAMMOTH TEETH

Mastodons and mammoths are extinct proboscideans, a group animals that includes the present-day elephants. 

This excellent image, which is from Wikipedia.org, shows how the general body of a mastodon (on the right) differed from that of a wooly mammoth (on the left, which could be up to 13 feet tall and weigh up to 8 tons). Mastodons were somewhat smaller had shorter legs, more muscular bodies, and a sloping (rather than a bulbous) head. 

Mastodon species inhabited North and Central America in the Pliocene, up to their extinction at the end of the Pleistocene, 10,000 to 11,000 years ago.

Mastodons ate coarse vegetation (twigs, leaves, roots, etc.) than did the mammoths. The evidence is provided by the shape of their molar teeth. As shown in the following image, they are cusp-shaped and were designed to crush coarse vegetation.

     A plaster replica of mastodon teeth (about 5 inches height). 



Mammoth teeth, in striking comparison, consist of a series of enamel plates, designed for chewing leaves and other "soft" vegetation (e.g., sunflowers, milkweed), or possibly even grasses. The latter contains silica, which would wear down teeth unless they are constructed in these parallel enamel plates, as shown in the following image.

    A plaster replica of a mammoth tooth (about 6.5 inches height).

Mammoth species were more widespread than mastodons and went extinct later, about 4,000 years ago.