2:45 PM - 3:00 PM
[MZZ42-05] Planning and practice of research and dissemination/education in line with the coring survey of Lake Harutori, Kushiro City
Keywords:Tsunami deposit, Lake Harutori, Pacific coast of Hokkaido, Educational activities, Lagoon sediments
From August 1 to 14, 2022, a coring survey of Lake Harutori was conducted using Grant-in-Aid for Scientific Research (A) 21H04523 with the support of the Kushiro City Board of Education and the Kushiro City Museum in Hokkaido. On the afternoon of Sunday, August 7, 2022, which is the middle day of the survey schedule, the Kushiro City Museum, the host of the our survey, conducted the HARUTORIKO geotour. In this presentation, the outline of the planning and practice of dissemination and education according to the research activities in cooperation with the museum is reported.
In our plan of the geotour, we focused on nature of Lake Harutori, which is a place of recreation and relaxation for Kushiro citizens, and examined the plan while adhering to three geo themes as bellows.
(1) Topography, geology and landslide hazards around Lake Harutori
First, we explain the topography and strata that can be observed along the lakeside promenade of Lake Harutori such as the sedimentary rocks deposited 40 million years ago (Urahoro Group), topography such as marine terraces and landslides 125,000 years ago. The Urahoro Group is a coal seam representative of Hokkaido, and the coal reservoir adjacent to Lake Harutori has supported the economy of Kushiro City as a major local industry for many years. On the other hand, the Konsen coastal area is known to be a landslide area, so we explain geoinfrmation for residents.
(2)Formation process of Lake Harutori
Second, Lake Harutori is a marine lake that preserves the morphology of the dissected valley formed during the last glacial period. Over the past 10,000 years, Jomon transgression has changed the environment from estuaries to inner bays to lagoons. In addition, in the current brackish water environment, seawater flows in from the mouth of the Harutori River at high tide, forming a two-layer structure consisting of a freshwater layer (surface layer) and a saltwater layer (bottom layer). Therefore, it is described that it is a valuable lake where the verved lamina is formed. A survey using the Mackereth piston corer is demonstrated.
(3)Traces of the great tsunami hidden under the lake bottom
Third, it has already been reported that there is a high possibility that Lake Harutori holds the history of earthquakes and tsunamis that occurred in the Kuril subduction zone over the past 10,000 years. We explain varve lamina and tsunami deposits on site using core samples. Since the event was held under the measures against the new corona infectious disease, we initially accepted applications for participation in this geotour from Friday, July 22nd on a first-come, first-served basis up to 30 people via the web or telephone. After that, there were also requests from science teachers in Kushiro City to participate, and in the end there were 37 participants, which was slightly more than planned. Most of the participants were residents of Kushiro City or neighboring areas. We heard that some of them came all the way from Tokyo to participate in our geotour.
The weather on August 7th (Sunday) was favorable. As planned, we gathered at the Kushiro City Museum at 13:30 pm and walked the 2.5 km route from the Kushiro City Museum, through the shore of Lake Harutori to the mouth of the Harutori River for 2.5 hours. We were able to finish without any major problems.
Although we were not able to ask participants about their impressions of participating in this geotour in detail, we believe that they were highly evaluated overall. It is important for us to hear from junior high and high school science teachers in Kushiro City that they would like to use the route of our geotour that we presented this time as an educational training of the school.
This geotour was planned as part of the outreach activities of Grant-in-Aid for Scientific Research (A) 21H04523. We would like to express our deep gratitude to Dr. Hirokuni Oda of GSJ/AIST, Dr. Kota Katsuki of Shimane University, Dr. Toshinori Nakanishi of Museum of Natural and Environmental History, Shizuoka, and all those involved for their cooperation.
In our plan of the geotour, we focused on nature of Lake Harutori, which is a place of recreation and relaxation for Kushiro citizens, and examined the plan while adhering to three geo themes as bellows.
(1) Topography, geology and landslide hazards around Lake Harutori
First, we explain the topography and strata that can be observed along the lakeside promenade of Lake Harutori such as the sedimentary rocks deposited 40 million years ago (Urahoro Group), topography such as marine terraces and landslides 125,000 years ago. The Urahoro Group is a coal seam representative of Hokkaido, and the coal reservoir adjacent to Lake Harutori has supported the economy of Kushiro City as a major local industry for many years. On the other hand, the Konsen coastal area is known to be a landslide area, so we explain geoinfrmation for residents.
(2)Formation process of Lake Harutori
Second, Lake Harutori is a marine lake that preserves the morphology of the dissected valley formed during the last glacial period. Over the past 10,000 years, Jomon transgression has changed the environment from estuaries to inner bays to lagoons. In addition, in the current brackish water environment, seawater flows in from the mouth of the Harutori River at high tide, forming a two-layer structure consisting of a freshwater layer (surface layer) and a saltwater layer (bottom layer). Therefore, it is described that it is a valuable lake where the verved lamina is formed. A survey using the Mackereth piston corer is demonstrated.
(3)Traces of the great tsunami hidden under the lake bottom
Third, it has already been reported that there is a high possibility that Lake Harutori holds the history of earthquakes and tsunamis that occurred in the Kuril subduction zone over the past 10,000 years. We explain varve lamina and tsunami deposits on site using core samples. Since the event was held under the measures against the new corona infectious disease, we initially accepted applications for participation in this geotour from Friday, July 22nd on a first-come, first-served basis up to 30 people via the web or telephone. After that, there were also requests from science teachers in Kushiro City to participate, and in the end there were 37 participants, which was slightly more than planned. Most of the participants were residents of Kushiro City or neighboring areas. We heard that some of them came all the way from Tokyo to participate in our geotour.
The weather on August 7th (Sunday) was favorable. As planned, we gathered at the Kushiro City Museum at 13:30 pm and walked the 2.5 km route from the Kushiro City Museum, through the shore of Lake Harutori to the mouth of the Harutori River for 2.5 hours. We were able to finish without any major problems.
Although we were not able to ask participants about their impressions of participating in this geotour in detail, we believe that they were highly evaluated overall. It is important for us to hear from junior high and high school science teachers in Kushiro City that they would like to use the route of our geotour that we presented this time as an educational training of the school.
This geotour was planned as part of the outreach activities of Grant-in-Aid for Scientific Research (A) 21H04523. We would like to express our deep gratitude to Dr. Hirokuni Oda of GSJ/AIST, Dr. Kota Katsuki of Shimane University, Dr. Toshinori Nakanishi of Museum of Natural and Environmental History, Shizuoka, and all those involved for their cooperation.