From this overlook, if you look south along the beach at the bottom
of the cliffs you will see some interesting rock terraces, which
are in fact ancient seas floors which have been formed into marine
terraces. These terraces are thought to be created by a combination
of powerful forces.
The first force is the sea itself, which helps to create the
flat, relatively smooth tops via the relentless pounding of the
ocean's waves. During glacial periods, the sea level drops
considerably and water retreats, only to advance again as the Earth
warms, and that action creates wave-cut marine platforms.
The second force is seismic. Here in Santa Cruz, the Pacific
Plate, part of the "Ring of Fire", is moving northward, while the
San Andreas Plate is moving southward, combining for about two
inches of movement per year. Nervous local geologists began
studying the movement in the era of the 1906 earthquake, and for a
time there was a beacon on top of Loma Prieta that was used to
measure the mountain's extremely rapid (in geological terms)
movement.
Locally, these two mighty plates meet at the where there is a
bend in the San Andreas Plate around Loma Prieta, and as a result
the Pacific Plate is slowly forced upward over the San Andreas
Plate. This uplift activity creates the Santa Cruz Mountains and
lifts these marine terrace layers upward as well. The uplift is
approximately .3mm per year.
The Santa Cruz area comprises five such marine terraces. If you
look at most of Santa Cruz, you'll notice that it's a relatively
flat landscape separated by steep bluffs from the adjoining
terraces. Other marine terraces can be found along the California
coast and beyond, the oldest (and highest) being approximately one
to two million years old.
The Seymour
Marine Discovery Center here is a great place to come with the
family. They offer daily tours. Admission to the area is free and
open to the public but the museum itself charges admission. Please
check their website for current information on hours.
To log this cache there are two requirements (Revised 2/3/07)
- Please read them carefully!:
- Take a picture of yourself, holding your GPS, at the location
and post it along with your log. I must be able to tell from the
picture that it's you at the location (no background of just sky
from now on) to verify that you were there.
- Go to the railing of the overlook, and face south. Take a good
look at the marine terraces here. In your log or in email to me
(your choice) you must estimate how high the cliffs are above the
flat terrace rocks below. If you do not, I will be forced to delete
your log. This educational aspect is required for all EarthCaches
and this one would have been archived had I not added this
requirement.
If for some reason you can't immediately post the picture,
post your log as a Note rather than a Find until you have done so.
Finds logged without the exact requirements being posted within a
reasonable amount of time (like a day) will be deleted. You can't
say you weren't warned, right? :)
Bibliography and additional reading:
- James F. Tait, Coastal Geology of
Natural Bridges State Park
- Jennie Munster and Jennifer W. Harden, Physical Data
of Soil Profiles Formed on Late Quaternary Marine Terraces near
Santa Cruz, California
- Colin Pinney et al., Soil Chemistry and
Mineralogy of the Santa Cruz Coastal Terraces
- California's
Marine Terraces, an excerpt from the California Coastal
Commission's California Coastal Resource Guide
- John V. Young, Ghost Towns of the Santa Cruz
Mountains
Content revised 7/8/05
Bonus info! Did you notice the old weathered remnants of a mast
on the edge of the cliff there behind the discovery Center, just a
little south of this Earthcache? I found some history about it from
the datasheet for the nearby benchmark,
in an entry from way back in 1931: "A SHIP WAS WRECKED ON THE BEACH
ABOUT 30 FEET S OF THE STATION. A MAST SAID TO BE USED FOR HOISTING
THE CARGO FROM THE WRECK IS STANDING UPRIGHT ON THE EDGE OF THE
CLIFF S OF THE STATION. THE TOP OF THE MAST PROJECTS ABOUT 10 FEET
ABOVE THE TOP OF THE CLIFF."
