Editor’s note: First of two parts.
This week I review our ever-changing planet from what I have seen and experienced and read about in scientific journals.
With our new adventures in outer space we are now finding that our neighbors in our solar system are also changing, as we – planet earth – are changing. In my lifetime I have experienced very severe earthquakes that brought minor and major changes to planet earth.
My most vivid memory was sitting in my schoolroom on the second floor in the 5th or 6th grade in Everett, Wash. The teacher had us waiting for the school lunch bell at noon. Papers had been put away. She was sitting at her desk, giving last-minute instructions for afternoon study. In my school days, we had large classes – 32-36 students. At 11:56 a.m., on April 13, 1949, the building started to rock. We had two rows of five lighting fixtures that hung on chains from the ceilings. The chains were probably about 4 feet long. As the motion increased, these light fixtures started to do the swaying dance. Our teacher broke into tears, the girls screamed, and the boys laughed. It was one of the strongest earthquakes to occur in modern times in the Pacific NW. It was a 6.7 on the Richter scale. The number was later increased to 6.8. It was centered on a large fault in the Nisqually Valley, which lies NE between Tacoma and Olympia. My school did not suffer any damage. The grade school Jean had attended did suffer some damage. There were a reported 64 injured and 8 killed. Four of those deaths were caused by heart attacks. The other four were from falling objects. The damage was significant – in the millions of dollars – in the Seattle/Tacoma/Olympia/Auburn areas. There was damage reported throughout the NW, as far as British Columbia. The quake was felt in Idaho and Oregon.
In 1965, on April 29, we were shaken out of bed at 8:28 a.m. by a 6.7 earthquake. I was on swing shift at the time. We woke up to the bed dancing across the floor. That earthquake was centered between Seattle and Tacoma, on the same fault zone as the 1949 Nisqually quake.
Again, in 2001, part of the same fault zone shifted and created significant damage in the Shelton, Wash. area and caused major damage to bridges and Highway 101.
The strongest quake to hit the U.S. states was the 1964 Alaska quake that carried a magnitude of 9.2, and the duration was 4-5 minutes. This quake was created through the shifting of the Pacific Plate and the North American Plate.
Portions of Alaska near the quake raised 20 feet.
On Aug. 17, 1959, at 11:35 p.m., Sheep Mountain split in half. It is on the west side of the Madison River Valley in SW Montana. Literally, the east side of the mountain came down across the valley, 5½ miles, carrying rocks, debris the size of large cars. It covered portions of two campgrounds and blocked the Madison River. The depth of debris across the river was in excess of 200 feet. It trapped 259 campers between Hebgen Dam, upriver, and the slide. It is estimated that over 80 million tons of rock moved in that one giant motion. This quake was recognized as one of the largest to hit anywhere in the Rocky Mountains and the Continental Divide, as well as the entire USA. The Valley suffered 18-20 feet offset.
The slide created winds over 80 mph, as it rolled across the Madison Valley and up the far side. There were somewhere around 25 lives lost.
Most of the 259 people trapped made it to high ground and were rescued by helicopter and emergency corps of engineers.
The Hebgen dam was constructed in 1927, and those familiar with earthquakes and the shifting of earth in the valley at that time were amazed that the dam held. The slide forced water upriver and went over the top of the dam in excess of 10 feet.
Today, the core of engineers have opened a permanent channel draining the earthquake lake. The lake today is three-quarters of a mile wide and 6 miles long.
The Corps of Engineers immediately opened a temporary channel so the river would not back up over the top of the dam and flood West Yellowstone, 27 miles upriver.
This quake occurred approximately 27 miles from west Yellowstone. It changed the eruption pattern of several geysers and opened up long-dormant geysers at that time.
I don’t have any information as to lasting effects in Yellowstone Park.