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Sat, Sep 11


Alum Rock Park

Seniors Hike for Health

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Seniors Hike for Health
Seniors Hike for Health

Time & Location

Sep 11, 2021, 9:00 AM – 11:30 AM

Alum Rock Park, 15350 Penitencia Creek Rd, San Jose, CA 95127


About the Event

Come enjoy a gentle stroll along this flat all paved meandering trail. Mostly shaded by the native oaks and sycamore it’s a great place to escape and enjoy the geologic wonders of nature together.  Be sure to bring water and a hat. Sandwiches are provided for free. There is no cost to park at Rustic Lands parking lot.

Established in 1872 but serving as public land since the pueblo was established in 1777 Alum Rock Park is California's oldest municipal park! It received its current name around the turn of the 20th century when thenardite-containing rocks near its entrance were mistaken for alum.

Its proximity to the convergence of the Hayward and Calaveras faults make this region of the Diablo Range a geologic wonder. We love it’s natural and cultural history and really dig the mineral springs.

A spring is a place where water moving underground finds an opening to the land surface and emerges, sometimes as just a trickle, maybe only after a rain, and sometimes in a continuous flow.

Thermal springs or “hot springs” are normal springs except that they are warm or sometimes hot. They occur in regions of recent volcanic activity and are fed by water heated by contact with hot rocks far below the surface. Even where there has been no recent volcanic action, rocks become warmer with increasing depth. Water may migrate slowly to considerable depth, warming as it descends through rocks deep in the Earth. If it then reaches a large crevice that offers a path of less resistance, it may rise more quickly than it descended. Water that does not have time to cool before it emerges forms a thermal spring.

The valley has abundant mineral springs, which were touted as beneficial to people's health. In the late 19th century and through the 1930s, the park was famed throughout the country as a health resort advertising hot and cold sulfur, soda and magnesia springs, as well as mixtures of sulfur, soda, magnesia, arsenic, iron, and their sulfates. Grotto stonework are around many of the mineral springs.

The 2007 Alum Rock 5.6 earthquake hit the Bay Area at 8:04 pm. One effect of the earthquake was to cause a previously dried spring to begin flowing again.

Briones sandstone is a sedimentary rock originally formed in a marine environment. Alum Rock Park was an ocean beach 15 million years ago. Three kinds of ancient clam shells are embedded in the rock, cemented in place by calcium carbonate.

Address: 15350 Penitencia Creek Rd, San Jose, CA 95127

Directions: Traveling on Hwy 101 North. Continue on 101 N. Take I-680 N to McKee Rd. Take exit 2B from I-680 N

5 min (5.1 mi). Continue on McKee Rd. Drive to Penitencia Creek Rd 8 min (2.8 mi). 

Parking: Rustic Lands parking lot (free to park in this lot, do not pay at kiosk)

Meeting Location: Rustic Lands parking lot

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  • Seniors Hike for Health

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