Columbia River Basalts

About 5 to 25 million years ago one of the largest flood basalts ever to occur on earth happened in the Pacific Northwest.   These flood basalts spread across what is now Oregon, Washington and Idaho.   There have been arguments that  they even extended into far northern California and Nevada.   In either case, they were huge and cover about 63,000 square miles.   Scientific analysis of Argon and Potassium in these basalts indicate that the largest eruptions were from 17-14 million years ago and to a lesser extent from 14-6 million years ago.

The estimated volume of these basalt floods is over 41,500 cubic miles.  While this is very large in human terms, it is not so in geological terms.  It would take over 12,500 of these floods to equal the volume of the moon.

Here is a map from the Large Igneous Province Commission that shows the extent of these floods.  The asterisks on the map show the location of the Cascade volcanos.   

 

I first saw some of the features of this great province on a trip from near the California and Oregon border  up Highway 395 on my way to Golden, Alberta, Canada.   About 30 miles north of Lakeview, Oregon is Abert Rim and Lake.   John Fremont discovered Abert Rim and Lake on December 20, 1843 and named it for his commanding officer The rim rises about 2,500 feet above the valley floor and can be seen for about 30 miles.    Below it is one of the largest lakes in Oregon.   I was totally fascinated by the view into earth's geologic past.   The top 500-600 feet of the rim are almost vertical and the huge basalt cap of the rim is clearly evident.   Here are two photos I took at the time.

Abert Rim 

 

Abert Lake and Rim

 

Technorati tags: Geology, flood basalts

Geodes in Keokuk Iowa

In the 70's my wife, Anita, and I took a long 4th of July weekend and drove down to Keokuk Iowa. We were going to find geodes. Actually, we never looked for them in Iowa. We stayed at a motel there and used it as our base for this adventure. We had been advised that when it came time to go looking and collecting, we should go across the river to Hamilton Illinois.

A fellow rock hound had advised us of a gravel quarry near Hamilton that would be a great collecting site. After asking directions locally, we crossed over the river and found the quarry.

It was the 4th and no one was at the quarry. It was deserted and there were no signs telling us to stay out, so Anita wrote a note and left it on the gate thanking them for allowing us in and left our names.

I had two strong cardboard boxes that once had held reams of copy machine paper. We dragged them down into the quarry and began searching. It was a geode hunters paradise. They were everywhere. All we had to do was to remove them from the dirt walls of the quarry. After a couple of hours we had one box full and I lugged it back to the car.

It was about 107 degrees out and we were tiring. Anita decided to leave the area where we were working and take a walk around the floor of this huge quarry. I continued collecting and after about 15 minutes I heard her shouting my name in a voice filled with panic.

I ran to when she had disappeared and when I rounded the corner I saw her problem. She had found a shallow pool of water about 50 feet across and had tried to wade through it. Now she was stuck half way to her knees in mud.

Trying hard not to laugh I was able to get her out with only minor effort. But now we were both mud from our necks down. That effort as well as the heat had us beaten. So we gathered up the half filled second cardboard box and went back to the motel for a well deserved shower and long nap.

For the next 15 years I gave away all of those geodes except for one that I keep in memory of that crazy weekend. Of course this story frequently accompanied the geode.

Rocks Are Not Hard Stuff

Geology became mainstream when John McPhee began writing about rocks. His Pulitzer prize winning book Annals of the Former World is an easy read for anyone even remotely interested in America, rocks, geology, or interesting people. It is all in there and it is beautifully written. He is one of my favorite writers. If you want to learn more about rocks, without studying, read this book. A trip across America anyone can take.