Such an interesting place, Yosemite. We visited El Capitan, and saw lots of climbers all over it. When we looked more closely, some were photographing the rockface - we assumed they were taking shots of wildlife, but later saw a poster describng this project. Good to see the outcome.
I do not know what, in the rock types colour chart the term "dikes of the sea means." A dyke is a vertical (ish) intrusion of one igneous rock into any other rock structure. However "dikes of the sea" seems a bit vague in usual UK geological terminology as it does not accurately describe the type as in chemical composition, of the particular igneous rock that has been intruded.
The accurate chemical composition could easily be obtained from a sample and that could give more information about where the lava that dyke was made of was formed within the earths crust.
Which is totally fascinating to geology enthusiasts if no one else.