Sentinel Gap facts for kids
Sentinel Gap is a special place in Washington state where the mighty Columbia River cuts right through a mountain range called the Saddle Mountains. It's like a giant natural doorway carved by the river over a very long time. You can find it close to the town of Mattawa.
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What is Sentinel Gap?
Sentinel Gap is known as a "water gap." This means it's a valley or a pass that a river has carved through a ridge or mountain range. Imagine a river flowing along, and as mountains slowly push up, the river keeps cutting down through them, staying in its path. That's exactly what happened here with the Columbia River and the Saddle Mountains.
How Sentinel Gap Was Formed
The formation of Sentinel Gap is a cool story of nature's power. The Columbia River was flowing in this area even as the Saddle Mountains were slowly rising. The river was strong enough to wear away the rock at the same speed the mountains were lifting. This process is called erosion, which is when natural forces like water or wind break down and carry away rock and soil.
The Role of Ice Age Floods
Sentinel Gap also played a huge part during the ancient Missoula Floods, which happened during the Ice Age. These were massive floods, much bigger than anything we see today! Water from the Channeled Scablands (a unique landscape created by these floods) needed a way to reach the Pacific Ocean. Sentinel Gap, along with another place called Wallula Gap, became a main path for these floodwaters.
The floods were so powerful that they "reamed out" the gap many times. This means the rushing water probably made the gap wider and its walls steeper. If you look closely at the basalt rock walls of the gap, you can still see lines called strandlines. These lines are like ancient watermarks, showing the different levels the floodwaters reached!
What You Can See at Sentinel Gap Today
Today, Sentinel Gap is a busy and important area.
Transportation and Dams
- SR 243 is a road that runs along the east side of the Columbia River right through the gap.
- The Beverly Railroad Bridge crosses the river here, allowing trains to pass through this natural opening.
- The gap is located between two large dams on the Columbia River: the Wanapum Dam and the Priest Rapids Dam. These dams help control the river's flow and generate electricity.
Submerged Rapids
The Priest Rapids, which the Priest Rapids Dam is named after, used to be a set of fast-flowing parts of the river. However, they are now submerged (covered by water) beneath the dam's reservoir (the lake created by the dam). They are about 4 miles downstream from Sentinel Gap.
