Geology Klamath River

lower klamath lake formed in basin , range area of upper klamath river watershed.

pre-quaternary, igneous , sedimentary rock compose yonna formation, crosses of region , rises above surface in large outcroppings of solid rock in many of ridges. underlying rocks younger east west. many ridges crossing upper klamath basin divide valleys 330 feet (100 m) of vertical relief, , drainage patterns follow topography. extensive geothermal system occurs deep underground within upper basin, creating hot springs , artesian springs, not understood. further south, in shasta river area in siskiyou county, of underlying rock composed of lava flows issuing mount shasta volcanic region.

the same age pattern true in cascade range , klamath mountains cover western half of klamath river watershed. north american plate moved southwestward on past 10 million years, successive oceanic terranes dating cambrian late jurassic added bulk of north american continent. there 4 distinct terranes west east. while coastal mountains date less 3 million years ago, farther inland high cascades old 7.5 million years. granite batholiths, overlying sedimentary rock, , volcanic rock crumpled massif of southwestern oregon , northwestern california. instead of being diverted southwards, however, klamath continued flow westward , created steep-walled gorge through rising range. 1 of these terranes brought long north–south running band of eroded mica lies 30 miles (48 km) inland pacific coast of northern california. when klamath encountered layer, began cutting canyon along mica instead of continuing southwest pacific, resulting in sharp northward bend trinity river joins. lower trinity follows portions of mica , south fork well.