Time to talk soils
The soil at Montinore Estate in the Northwest corner of the Willamette Valley, is loess from the Missoula Floods. The Missoula Floods… well that takes us back a bit further in history, like 13,000 to 15,000 years back. During our interview with Rudy Marchesi, Immediate Past President and Partner at the winery, he took us into the tasting room to show us the beautiful Willamette Valley map created by the Willamette Valley Wine Association. Here he took a minute to paint the picture for us of the floods and the soils that came from these floods
The Missoula Floods
At the end of the last ice age, there was an ice dam in the Clark Fork River in what is now Idaho. This backed up the water from a finger of the Codilleran Ice Sheet that was melting and creating the Glacial Lake Missoula. As the water pressure built, the ice plug was forced upwards releasing cataclysmic flood waters, a wall of water 500 feet tall down the Columbia River to the ocean. After the surge of water, the plug would drop back into place and the lake would refill. Then periodically, the plug would get pushed up and more flood water would be released. This repeated dozens of times over about a 2000 year period. The area that was flooded covered almost half of what is now Washington on it’s eastern side side of the state and followed the Columbia River to the ocean. It also branched off at the mouth of the Willamette River creating a lake that covered much of the Willamette Valley as far south as Eugene. Mind you, Glacial Lake Missoula was in Montana…yet another Montana and Oregon link for Montinore.
I found this link to an article on Oregon Live that discusses the flood
Here you can also find beautiful lidar maps (as Oregon Live puts it “think radar, but with light”), some of which are truly artworks, including an interactive mapthat illustrates the floodwaters by the Oregon Department of Geology and Mineral Industries
Build up of soils
Every time that the floods happened they would take out forests, that had grown in the last 75 years and carry that sediment with them, as well as anything else in their way (ie rocks, mammoths). Then the plug would drop back into place and the soil over the flooded area would dry out. Some of this would be dusty and dry, so the wind would carry it (wind blown loess). You have layers and layers of these soils, forests that were buried or swept away downstream. One of the ways they were able to tell that there were multiple floods, was because they found separate layers of ash from Mt. Saint Helens eruptions.
The soils of Montinore and the proposed Tualatin AVA
We mentioned that when the Chehalem Mountain AVA formed that they offered to include Montinore. Rudy declined. He knows his soil and it is different from that of the Chehalem Mountain AVA. The soils here are considered Laurelwood and Cornelius (wind blown loess glacial lake sediment) and are similar to some of those found in the Northeast part of the Chehalem Mountains, the area that is looking to become a nested AVA inside Chehalem, the proposed Laurelwood AVA.
So what does Rudy believe sets this area apart to warrant it’s own AVA? Well the windblown loess for a start. The loess is the fine topsoil that formed as the flooded areas dried out. These fine particles which include clay (the finest and lightest of particles), were blown westward and got caught by the hills. This dust buried an ancient redwood forest 200 feet deep. Rudy told us that he has had neighbors drill wells and pull up chunks of redwood from deep underground.
While it shares the Laurelwood soil series with the Chehalem Mountains AVA, the proposed Tualatin Hills AVA is located within the rain shadow of the coastal range and the temperatures are a bit higher.
Tualatin Hills AVA borders
The proposed AVA is a horse-shoe shaped basin that opens to the east, bounded by the Tualatin River watershed. To the northwest the boundry is the peaks of the coastal range, where the prevailing winds come over and hit the Chehalem Mountains and Portland. Then Willamette Valley AVA provides another border and urban development the last. Elevation borders sit at 200 feet for the low end (anything below that has soils to fertile for growing wine grapes) and 1000 feet on the high end, which is the natural boundry for growing wine grapes in this climate.
The overall proposed Tualatin Hills AVA covers 144,000 acres.
Stick with us as we continue our discussion with Rudy as we dig deeper into the soils and how the Missoula Flood Loess affects the flavors in the wines.
You can also check out our previous post Montinore Estate – a Recent History which tells how the Estate came by it’s name and the history of the property and winery.
This is really fascinating. We knew about the Missoula floods but had never heard about the proposed Tualatin AVA until you wrote about it. Very curious to learn more!
There are 5 proposed AVAs in the Willamette Valley currently. We managed to visit 4 on our trip. Rudy Marchesi was so generous with his time, talking us through the AVA, the Montinore Estate and it’s wines. And I must admit that I love learning about the soils.