I bet this may come as a surprise to many, but San Diego has it's own volcano that was active 15 million years ago! But that is not all. The Lake Calavera area also boasts a lake and dam dating back to the World War II era, multiple stone labyrinths and even a cave!
Preserve: Calavera Lake, meaning 'skull' in Spanish, offers 110 acres and over 4 miles of hiking and bike trails in Carlsbad. The reservoir is 400 acres and managed by the Carlsbad Municipal Water District. The entire area is habitat to an identified 115 plant, 49 bird, 10 mammal and 7 amphibian/reptile species. Of these identified species, 6 are classified as threatened or endangered. Among the area's endangered species are the Thread-leaved Brodiaea, Orange-throated Whiptail and the California Gnatcatcher. The California Gnatcatcher is perhaps the most threatened of these species because 85% of it's natural habitat, the Diegan Coastal Sage Scrub, has been destroyed by development.
Cave & Volcano: As for the cave.....well, it turns out that it's actually an old exploratory mine, known as an "adit". This adit was mainly used as a rock quarry for valuable minerals. The Calavera Hills contains a volcanic plug which is found throughout North County San Diego.
The plug contains a fine-grain basalt which actually clogged the volcano's throat millions of years ago. After its last eruption, the cone slowly eroded, leaving only the plug. For almost 25 years, miners used the plug to mine gravel, speeding up the erosion process.
Without being radiometrically dated, the volcanic plugs are thought to have formed in the Miocane, when our coastline was transitioning from a convergent plate boundary to a transform plate motion. This transform motion is what eventually formed the San Andreas fault.
Fishing: Although fishing is allowed here, from what I am gathering on the internet, it is not an ideal fishing spot due to lack of permitted fishing areas. Here's a good site to see what fish you can catch here: http://www.fishingnotes.com/fishing-report/ca/Calavera-Lake
Labyrinth: Coordinates: 33.168833, -117.284051 Before heading out here, take a good look at Google Maps on satellite to see where the labyrinths are. There are 3 that we know of although there may be more on top of the mountain. Who created them is a mystery to us at this point.
There's a cool spot for skateboarders that you'll walk by:
Here's the volcano!At the base of the volcano is a stacked rock garden and several labyrinths:
Update: The cave has unfortunately since been sealed by the city. Here are some photos of what it looked like though:I'd say you could fit 8 or 9 people comfortably inside:Beautiful patterns inside:
And what it looks like now:
We decided to climb to the top to see what we could find. Pretty nice view!
We found "Bob's Garden" up top:
We also found old pipes and a collapsed road in the canyon: