From: Winnipeg, MB
I wonder if that is related to all the ground shifting associated with Kilauea's eruption. There has been much activity all around the Pacific Ring of Fire over the past several weeks.
For Geologic activity Oahu and Kilauea are pretty far apart. The distance from Hilo to Honolulu is 337 Km (209 Mi). That's close to twice the distance between Mt St Helens and Seattle.
Also Hawaii is not part of the Ring of Fire. It's a completely different type of volcano. Most volcanoes are inland from subduction zones where ocean floor is sliding under a continental plate. The Pacific is shrinking because the Atlantic is growing, so there are a lot of subduction zones where the Pacific Plate is getting eaten. The Philippines, Japan, the Aleutians, and the Solomons are all caused by subduction zones. The Pacific NW volcanoes are caused by a small plate called the Juan de Fuca plate that is being squeezed between the Pacific and North American plates.
The Hawaiian volcanoes are in the middle of the Pacific Plate. It comes from an ancient hot spot. Hot spot volcanoes happen where the crust cracks and essentially the mantle leaks out. The lava tends to be thinner and flows more easily than subduction volcanoes. These types of volcanoes are usually less violent, but put on big shows compared to subduction volcanoes.
The Hawaiian hot spot has been there at least 100 million years. The Hawaiian chain continues as a string of underwater volcanoes across the Pacific until the disappear under the Aleutians. There is a new Hawaiian island forming SE of the big island of Hawaii. Iceland is another hot spot volcano.
Hot spot volcanoes don't tend to ever go away. They seem to exist for a long time, but because the plates move and the hot spots don't with respect to the core, they appear to move. The hot spot that created Iceland is thought to have originated on land in Siberia where it was the most dramatic volcano event in Geologic history. The lava flows are called the Siberian Traps. Traps is the Swedish word for steps and the mountains created look like mesas or steps. The lava flowed in Siberia for around a million years and came very close to extinguishing life on Earth. We have oil because of this event. The die off was so extensive the bacteria that normally decomposes corpses died too and the dead animals that died in the oceans were buried instead of decomposing. Over time their bodies broke down and made oil and natural gas. (Coal comes from dead trees that got buried.)
Because the plates moved the hot spot is now mostly under the Atlantic and it isn't spewing vast amounts of CO2 and SO2 into the atmosphere. SO2 when it combines with water makes sulfuric acid.
North America has a hot spot volcano too that formed about 14 million years ago in SE Oregon. When it was active in Oregon it covered all of eastern Oregon and much of eastern Washington with lava several thousand feet deep. North America has moved westward since then and the hot spot moved east where it's now under the Rockies which makes it one of the most dangerous volcanoes in the world. You have a volcano with thin, active lava that wants to flow, but it had a massive granite plug on top of it. It takes a long time to melt the granite plug and then when it does, it goes off with a boom that makes Mt St Helens look like a wet firecracker. That volcano is Yellowstone.
There was another volcano like Yellowstone that went off about 40,000 years ago on Sumatra. I believe this one was fueled by subduction, but it was still a big boom. Today it's a giant lake called Toba.
The Arizona Memorial may be developing cracks because the Arizona is collapsing. It is steel that has been submerged in shallow salt water for 75 years. I believe the structure is sunk into the bed of the harbor rather than using the ship for support, but the wreck might be shifting a bit as it falls apart and might be disturbing the foundations of the structure.
Very interesting stuff! Were you a pro geologist, Bill, or just someone interested in earth's history?
No matter how bad a situation is, you can always make it worse. - Chris Hadfield : An Astronaut's Guide To Life On Earth