What is the geology of the Sea Lion Caves in Oregon?

Question

I am looking for information on the sea lion caves in Oregon. I need to know what type of rocks are in the cave and how it was formed. It would also be helpful to know of any legends associated with the caves :)

Answer 1

http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Places/volcanic_past_oregon.html
Sea Lion Caves are reputed to be the largest sea-cave in North America, and is an outstanding example of erosion by waves in basalt.
Basalt:
Basalt is a hard, gray to black extrusive volcanic rock, mafic (rich in iron and magnesium), fine-grained, sometimes displays frozen gas bubbles (vesicular texture), and sometimes contains phenocrysts of feldspar (Ca-rich varieties), hornblende, pyroxene, biotite mica, sometimes quartz or olivine.

http://www.oregon.com/attractions/sealioncave.cfm
"History: The cave was discovered in 1880 by Oregon ship captain William Cox. … Officials at the caves estimate the cave began formation about 25 million years ago and now is the height of a 12-story building. … The elevator was added in 1961 to give people access to the basalt rock cave"

Answer 2

Fecal bacteria