This is an impressive geological area! Enjoy this section of the PHP. No need to bushwhack! There are trails leading to GZ.
"Plant populations on the gabbro soils at Pine Hill have evolved through natural selection to become species or subspecies that are uniquely adapted to the specific soil chemistry and climatic conditions present there. When a plant is limited to a single, defined geographic location and is found nowhere else, it is called an endemic. The Pine Hill gabbro island is just one of the many unique habitats within California, a state with more than 5,500 native plant species, 40 percent of which are endemic."
"Gabbro is a type of volcanic rock that is formed from magma rich in iron and magnesium and that is slowly cooled deep beneath the earth’s crust. The Pine Hill gabbro was lifted up to the surface during the formation of the Sierra Nevada mountains."
Source: https://www.sacvalleycnps.org/gabbro-island/