Joshua Tree - Rocks

Before I got a book on Joshua Tree National Park I didn't realise that the Park is just as famous for the pillowy solidified magma as it is for the Joshua Trees themselves. In fact the more I looked the more I saw of this rock, even as far north as Kelso Dunes.

Geologists believe that millions of years ago there was an upward surge of magma (monzogranite) into the mountains (gneiss - pronounced 'nice') above, but it never broke the surface to become a volcano, apart from (very recently) at Amboy Crater. Then over the millenia the surrounding rocks were eroded in places by enough to reveal the monzogranite. I was reminded of the rocks that come together to make the Rock Monster in Galaxy Quest.

In the more Joshua Tree populous western side, the desert floor is at about 4500ft, and the outcrops are 100ft above, which make them so nice to photograph.

If you do the Ryan's Mountain climb, you'll see that these rocky outcrops although impressive from desert level are actually dwarfed by the surrounding mountains.


Another interesting feature are the Broken Terrace Walls, caused when magma newer than the monzogranite pushed into faults and fissures in the monzogranite.

In other places lighter quartz coloured intrusions are visible.

One thing you could consider doing is having a GPS which allows you to save locations as Lat / Long. Then you can mark on Google Earth & Google Maps where you've been.