A hometown newspaper with a local office, local owners & lots of local news
A hometown newspaper with a local office, local owners & lots of local news
My two Alaskan grandkids, 4-year-old Kai and Cora, 18 months, play in Earthquake Park in Anchorage. The beach they are playing on is the remains of the collapse of shoreline cliffs that fell into the sea during the 1964 earthquake there.
Hello to another edition of "Look at that!" I have been on the run recently and found myself in Anchorage, Alaska, where two of my grandchildren live.
The last time I traveled was my first trip to Hawaii, where I was struck by the similarities in geology between the north shore of Oahu and the north shore of Lake Superior. Even though our north shore is about a billion years older, the similarities were striking.
I decided to look for any similarities in the Anchorage area and Carlton County but was more impressed with one big difference: EARTHQUAKES. I wondered if there had been any earthquakes in our area?
The Anchorage area is prime earthquake country. We even visited Earthquake Park and were able to see the damage that was done in the infamous 1964 earthquake that registered a magnitude 9.2, the strongest earthquake on record for North America.
Last fall, on Nov. 30, a 7.0 earthquake struck 25 miles under the Anchorage area and shook my daughter's house, my son-in-law's workplace, and my grandson's preschool.
When an earthquake is shaking you are supposed to drop, cover, and hold on.
Kai, my grandson, enjoyed the earthquake. He thought it was fun hiding under the tables while the building shook and groaned; he and his little friends pretended there were Ninja turtles jumping up and down on the roof.
Their teacher didn't think it was fun.
Minnesota is one of the quietest states, seismically, in the nation. Carlton County is even quieter than the state as a whole. We have polar expresses, tornadoes, floods and mosquitoes, but very few earthquakes.
According to the Minnesota Geological Survey, on average there have been about 20 measurable earthquakes - not caused by mine blasting - in the state since 1860; that is about one every eight years.
Earthquakes typically occur where continental plates meet: they collide, slip past one another, and dive under one another; these interactions cause quaking and shaking. We here in Pine Knot country are smack dab in the middle of the North American Plate, thousands of miles from plate boundaries, so why the few earthquakes we have had?
My drawing shows the location of our earthquakes since 1860 and the position of ancient fault lines. These old fault lines, where major rock formations from different times meet one another, are more like fracture zones rather than plate boundaries.
These fracture zones are weak spots in the crust and may be the source of our earthquakes.
The North American Plate is moving westward at less than an inch per year. The eastern boundary of this plate is in the middle of the Atlantic Ocean; we live on a huge plate (see my other drawing). As our plate is slowly being pushed west, it is thought that this pressure on the entire plate may cause movement at our Minnesota fracture zones, causing small and very infrequent earthquakes.
If you really want to experience an earthquake, you need to move to San Francisco or Anchorage ... or you could just sit in my living room when one of our many freight trains rumble past my house, and our china cabinet shakes like crazy.
Have a great week; let's pay attention to what is going on in our backyards, or what is not going on, and we might learn something.
The very curious FDLTCC science tutor Glen Sorenson was Minnesota Teacher of the Year before he retired from teaching science at Proctor High School after 30-plus years. He is an avid outdoorsman who most recently coached the Lumberjacks Nordic ski team.
