The Flourmill Volcanoes, also known as The Flourmills, are a small volcano range near the west boundary of Wells Gray Provincial Park in east-central British Columbia, Canada. Located north of Mahood Lake and west of the Clearwater River, they form part of the Wells Gray-Clearwater volcanic field.
Geography
Two volcanic centres form the range, namely Flourmill Centre and Spanish Lake Centre. During volcanic activity 3,000 years ago, the craters of two cinder cones were breached, and lava flowed out the south side into the pass between Spanish Creek and Flourmill Creek. The lava then dammed Spanish Creek, creating Spanish Lake, occupying about of the Spanish valley to the southwest. This lava flow averages thick. Both cones were built upon unweathered glacial material.
Spanish Lake Centre
Situated east of Spanish Lake is the northerly Spanish Lake Centre with an elevation of . It consists of an older major cone and two younger parasitic cones. The older edifice is breached in the southwest by two lava flows and contains an inner younger cone that is breached on its north side by a lava flow from a flank eruption. Both cones comprise unconsolidated irregular volcanic blocks with little agglutinate, with the inner cone incorporating weathered bipolar fusiform bombs.
The older of the two parasitic cones is situated on the eastern rim of the major cone while the younger cone lies on the eastern flank of the older parasitic cone. Both cones contain a higher proportion of agglutinate material than the major cone. The younger parasitic cone has a deep crater, which formed during the final phase of activity of the Spanish Lake Centre.
Lava flows from two flank eruptions travelled westward into the Spanish Creek valley. That on the northern rim of the Spanish Lake Centre flowed out of a breach in the outer wall to the west and inward through a breach in the north wall of the inner cone. A stream section through the flow indicates that it is thick. The second more extensive lava flow originated from the southwest wall of the inner cone and destroyed a large portion of the outer cone. The flow is of a thickness comparable to the north flow.
Flourmill Centre
The Flourmill Centre lies at the headwaters of Flourmill Creek and is the most southerly of the two Flourmill Volcanoes. It has an elevation of and rises above its base. Three overlapping cinder cones of slightly differing ages comprise the Flourmill Centre. The oldest cone lies on the northeastern side and is only partially preserved, with the southeastern side having been destroyed or buried by ejecta from subsequent eruptions. It consists of irregular volcanic blocks and rare bipolar fusiform bombs interlayered with vesicular agglutinate. A breach on the southeast side of the cone drained a central lava lake. The lava flowed southwest into the Spanish Creek valley, carrying rafts of agglutinate from the wall of the cone.
Renewed volcanism on the southwestern flank of the volcano created a parasitic cone composed of loosely consolidated vesicular volcanic blocks interlayered with agglutinate. Several well-preserved spherical and breadcrust bombs as well as poorly preserved bipolar fusiform varieties occur with the irregular volcanic blocks. A breach on the south side of the cone permitted drainage of a lava lake in the crater.
The most recently formed part of the Flourmill Centre is a well-preserved composite cone on the northwest flank. It partially overlies deposits from the southwestern vent and consists of loosely consolidated volcanic bombs pervasively interlayered with agglutinate. The crater is breached on the southwest side and contains the remnants of a lava lake. Late stage activity in the crater formed a small ring of extensively weathered scoriaceous ejecta on the northwest inner wall of the main crater.
Like the Spanish Lake Centre to the north, lava from the Flourmill Centre flowed into the valley of Spanish Creek. Three lava flows have been identified, each having a thickness of along Spanish Creek. The lava beds extend about down the Spanish Creek valley and have a maximum width of .