huckelberry wrote:DrW,
My imaginary presentation is also part of a slow personal coming to terms with basalt. I was a child who collected rocks when my family moved to eastern Washington. I found all rocks every where to be the same dark brittle fracturing basalt. Basalt basalt everywhere not a thing to find. As a child I thought the arrangement unfair. Older I have found there is some interest to be found in the stuff.
Huckleberry,
I agree that Eastern Washington is a great place to see the effects of geological forces. The fact that there is little natural vegetation and ground cover makes it easier to appreciate as well.
Basalt formations aren't all bad for rock hounds. There are areas where mineral laden water seeping through voids in fractured or vesicular basalt (mainly the latter) slowly leaves silica deposits that eventually build up to form agates.
In Idaho, some of these are released by erosion (or by highway construction) and make their way into the Snake RIver from which some are eventually deposited with the gravel where the river course turns at places like Farewell Bend near the Idaho / Oregon border.
My kids and I have scored an oatmeal box full of very nice, mainly white, agates at Farewell Bend in just a few hours of hunting when the river level is low in summer just after the spring run-off. We would always plan our trips with an agate hunting stop at Farewell Bend State Park.
In general, I found Eastern Washington to be a great place to go rock hunting. One can find obsidian, Ellensburg blue agates (probably rare now), and a lot of jasper, petrified wood, now and now and then even an arrowhead. Some of this material arrived after having been washed down from the Cascades and elsewhere and deposited there to be found in rock quarries, road cuts, river banks, etc.
If one looks a the literature on agates formed in basalts, the age of the basalt formations in question is often in the tens to hundreds of millions of years.
Wonder how YECs would explain the presence of large agates in basalt. Agate formation is a very slow process.
