Thursday, May 7, 2009

A Whatizit? Photo for the Day

A nice little photo "what is it?" for the day. The dark chunks are about a foot across and the location is at the south end of Joshua Tree National Park. I was going through the photo archives of one of my meetings of the National Association of Geoscience Teachers, preparing a post about our roadguide for the geology of the Coachella Valley and surrounding mountains. You can check it out here.

6 comments:

Callan Bentley said...

Xenoliths differentially weathering out of a granite?

Anonymous said...

Ironstone rip-ups differentially weathering out of a massive, coarse-grained (possibly arkosic??) channel sandstone?

--Howard (Calgary, AB)

Roy-Z said...

My guess is a series of xenoliths

Garry Hayes said...

Thanks, yes, these are xenoliths of metamorphic rock that have eroded in a somewhat unusual fashion from granite rock. The answer about arkose reminds me of my first field geology class; our prof took us to a site in Cajon Pass without establishing the context, and stuck us in front of an outcrop and asked what it was. We all agreed that it was an exposure of arkosic sandstone, only to find out that it was highly weathered granite.

Jules said...

In my imagination,but not in stated in geological terms it looks like an extreme close-up of a chocolate chip cookie with very large chunks of blocky and mouthwatering chocolate emerging from the cookie dough...sorry, I couldn't resist :)

Silver Fox said...

It *does* look a bit like a closeup of chocolate chip cookie dough. Mmm...