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Rogers Peak is the highest mountain in Tillamook County, Oregon.〔 Located in the Tillamook State Forest, the peak is also the highest peak in the Northern Oregon Coast Range, which is the northern section of the Oregon Coast Range.〔 (【引用サイトリンク】 North Oregon Coast Range )〕 == Geology == The origins of these mountains began approximately 40 million years ago during the Eocene age. During this time-period, sandstone and siltstone formed in the area. Additionally, igneous rocks and basalt flows combined with basaltic sandstone to create many of the mountainous formations. Other sedimentary rock in the area formed more recently, around 20 million years ago. It is hypothesized that portions of the area were islands during parts of the Eocene era.〔 (【引用サイトリンク】 Upper Nehalem Watershed Analysis )〕 The entire coast range sits on a convergent tectonic margin interacting with the Juan de Fuca Plate that is subducting beneath North America tectonic plate.〔 〕 The range is part of a broad, plunging structural arch of sedimentary and Tertiary volcanic strata that is being uplifted.〔(【引用サイトリンク】 Geologic Map of the Tillamook Highlands, Northwest Oregon Coast Range )〕 Other portions of the mountains consist of marine sedimentary rock.〔 〕 The basalt in the area comes from basalt flows that covered much of Oregon that originated from fissures in the central portion of the state.〔 It was during the middle Miocene period that the range was uplifted in the broad, northeast-plunging arch.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rogers Peak」の詳細全文を読む スポンサード リンク
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