An oxbow lake starts out as a “meander” in a river (like an S-shaped curve). It’s usually on a flat plain. A lake forms when the river finds a shorter, straighter route, leaving water behind in the S-curve.
when a meander becomes very pronounced,the outside bend or concave bend is so rapidly eroded that the river cuts through the narrow neck of the loop, forming an ox-bow lake or 'mortlake' (meaning dead lake). the river then flows straight. the ox-bow lake will later degenerate into a swamp through subsequent floods that may silt up the lake. it becomes marshy and eventually dries up.
The cascade volcanoes were formed by the subduction of the Juan De Fuca, Explorer and the Gorda Plate (remnants of the much larger Farallon Plate) under the North American Plate alone the Cascadia subduction zone
