****As of August 2023, most of the signs are missing or not readable. The county does not have plans to replace them as of this month, but you should be able to answer the questions with information on the cache page. ****
Located northeast of Corvallis at the north end of Lancaster Street, the wetland was established as a Benton County Park in 1992 to protect the natural features of the area and allow for education, research and public use.
Jackson-Frazier Wetlands lies in one of the lowest areas of the Willamette Valley, which is situated between the Coastal Range to the west, and the higher Cascade Mountain range to the east. It is a broad, long valley with the Willamette River coursing northward nearby.
Much of the Willamette’s fertility is derived from a series of massive ice-age floods that came from Lake Missoula in Montana and scoured across Eastern Washington, sweeping its topsoil down the Columbia River Gorge. When floodwaters met log-and-ice jams at Kalama in southwest Washington, the water caused a backup that filled the entire Willamette Valley to a depth of 300 to 400 feet (91 to 122 m) above current sea level. Some geologists suggest that the Willamette Valley flooded in this manner multiple times during the last ice age.
Over a period of thousands of years, the waters of Jackson and Frazier Creeks draining from McDonald State Forest have carried fine silts and clays, depositing them over a coarser silt layer dating to glacial times. The resulting clay-rich wetland soils shrink and crack in our dry summers, and in winter cracks swell shut and drainage is impeded. Ponding is common throughout the wetland from mid-November to mid-June. Water in creeks and remnant drainage ditches may be high. In some years the wetland dries out in May while in others it is still soggy in July.
In general terms, water seeps down from a rain-soaked surface, streams or rivers to an impermeable or less permeable layer of rock. A layer of rock or soil above this less permeable layer becomes saturated, hence it is called the saturated zone. The top of the saturated zone is called the water table. If the water is high here, it is considered at the top of this water table.
In order to log this earth cache, please email me the answers to the following questions. Do not enter them on your log or they will be deleted.
- What geological action caused this wetland elevation?
- What time of year is your visit? What is the water level, and can you explain why?
- Aside from rain water, how did the water here accumulate?
- Why is this a wetland vs. a swamp or catch basin?
Please enjoy the stroll on the boardwalk and the wonderful diversity of this natural gem.
This earth cache is placed with permission of the Benton County Parks Department. www.co.benton.or.us