Our training week is over and with a bit of free time before our volunteer work begins, Blue and I have been hitting Bullard’s Beach early in the morning. See if you can find him here. Don’t forget you can Click the Pictures to make it easier to see things.
The wind is calm at that time and the beach has few or no footprints. Over the last week three beautiful agates have presented themselves. This is the largest I’ve ever found.
Lanny walks the beach almost everyday. He says his goal is to live to be “a hundred”. In order to make his way back over the dunes to his truck he traces one of these lines as he heads to the beach and traces another as he leaves. When I see his line/s I know the beach has been scanned for the “good stuff”.
Collecting petrified wood is his passion. He tells me this area of Oregon coast is the most “fertile area” of the coastline as far as petrified wood goes and the larger the better. He also claims to have seen agates the size of bricks! I’d like to see that.
Today, among his regular finds he has something he doesn’t recognize. It looks like a coral but could be a petrified sponge. If you know what this is please let me know so I can tell Lanny next time I see him.
A Reader Responds:
I read your April 18th Blog entry and believe I have two possible explanations for the "mystery rock" found by Lanny at Bullard’s Beach.
First, I believe the sample is neither a petrified sponge or petrified coral. Both of these materials are very dense and are rarely carried very far by even strong ocean currents. Since the nearest indigenous Pacific sponges similar in shape and size to this sample are from the far Western Pacific and in petrified form would not travel very far; I have dismissed this as a viable candidate. I have also dismissed the possibility that this could be a petrified coral. Round or Brain Corals have very uniformly shaped indentations from the once living polyps. This sample lacks that characteristic.
I believe this "mystery rock" to be either a volcanic scoria or volcanic pumice. Both of these materials are types of basaltic rock that are produced by high pressure volcanic eruptions that contain large amounts of gas that is trapped within the melt at the time of solidification.
The best way to determine which type of rock this is; would be to test or approximate the specific gravity of each. Given that cold sea water has a specific gravity of greater than 1.2, a simple test would help to differentiate this sample.
Just immerse this sample in a bucket of cold sea water, and if it sinks to the bottom quickly – then it is most likely scoria. If it floats, or suspends in the water, it is most likely pumice.
Furthermore, if the sample floats it is probably a rarer type of pumice that is produced by underwater volcanoes. This occurs because the lava cools very rapidly and traps much more gas before solidifying resulting in the lighter weight.
I hope this helps!
Sincerely, Leigh Olsen
What a great bit of research, Thanks Leigh
Here’s another response from the founder of Shoreline Education for Awareness, Bill Russell:
The “rock” found by Lanny was the home of a colony of tube worms. It is the remains of an aggregation of Dodecaceria. See http://bio.classes.ucsc.edu/bio161/KFE%20invert%20photos/D_fewkesi.html for a view of a living colony. Attached is a scan of a couple of pages in “The Natural History of Ano Nuevo.”
This kind of low tide is what a beachcomber loves…a minus 2.1 tide. You find and see things unavailable most of the time. (note: I shot this picture the morning after this entry on 4-19-2011). Click it for a great view of the exposed sand which one rarely sees here. Oh yeah, Blue is there too!