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23-449: 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 10 km (6.2 mi) of the Spanish valley to

46-490: A crater lake . These lakes may become soda lakes , many of which are associated with active tectonic and volcanic zones. A crater may be breached during an eruption, either by explosions or by lava , or through later erosion. Breached craters have a much lower rim on one side. Some volcanoes, such as maars , consist of a crater alone, with scarcely any mountain at all. These volcanic explosion craters are formed when magma rises through water-saturated rocks, which causes

69-497: A phreatic eruption . Volcanic craters from phreatic eruptions often occur on plains away from other obvious volcanoes. Not all volcanoes form craters. Canadian Pacific Survey The Canadian Pacific Survey or Canadian Pacific Railway Survey comprised many distinct geographical surveys conducted during the 1870s and 1880s, designed to determine the ideal route of the Canadian Pacific Railway . Although much of

92-506: A beach estate on Vancouver Island from the Rath family for $ 186,000, then offered it to the provincial government in exchange for permission to log in Wells Gray Park. The government created Rathtrevor Beach Provincial Park from this arrangement, today one of British Columbia's most popular parks, and gave Clearwater Timber logging rights on 137 km around The Flourmills. The company built

115-405: A breach in the north wall of the inner cone. A stream section through the flow indicates that it is 7 to 10 m (23 to 33 ft) 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. The Flourmill Centre lies at the headwaters of Flourmill Creek and

138-408: A conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted as lava . A volcanic crater can be of large dimensions, and sometimes of great depth. During certain types of explosive eruptions , a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger depression known as a caldera . In most volcanoes,

161-539: A higher proportion of agglutinate material than the major cone. The younger parasitic cone has a 20 m (66 ft) 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

184-570: A road along the west bank of the Clearwater River to access this forest tract and during the next six years removed 6.8 million cubic feet of timber, valued at $ 1.6 million. The deal was cancelled by the NDP government after it was elected in 1972. The bridge at the Mahood River was removed in 1975, preventing access to The Flourmills from the east. The volcanoes were added to Wells Gray Park in 1997, at

207-412: 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

230-609: Is the most southerly of the two Flourmill Volcanoes. It has an elevation of 1,495 m (4,905 ft) and rises 250 m (820 ft) 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

253-604: The Coast Mountains icefields and a range of potential pass and route combinations, including new discoveries - the most notable and crucial of which was Rogers Pass through the Selkirk Mountains , but also less famously but no less crucially Eagle Pass through the Monashees . Routes investigated included those of the bronze rush-era Waddington's Road via Bute Inlet and the eventual Lillooet-Squamish-Howe Sound routing of

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276-665: The Flourmill Volcanoes was on May 21, 1874, by the Canadian Pacific Surveyor Joseph Hunter and three assistants. His diary describes their journey over the Flourmill lava flow: The Flourmill Volcanoes became a political scandal in 1963. Clearwater Timber Products, the major employer in Clearwater, wanted logging rights in Wells Gray Park. Rebuffed in several direct attempts, the company instead purchased

299-556: The Spanish Creek valley and have a maximum width of 2 km (1.2 mi). The unusual name 'Flourmill' dates to a land survey in 1921 along the Clearwater River. Flourmill Creek, which flows southeast from the volcanic area, was found to enter the Clearwater River exactly four miles (6.5 km) due north of the Mahood confluence. As such, it was named Four Mile Creek. When map-makers in the Department of Lands were tasked with placing this on

322-412: The base of the south cone and 0.5 km (0.3 mi) further to a section of the lava flow. Volcanic crater A volcanic crater is an approximately circular depression in the ground caused by volcanic activity. It is typically a bowl-shaped feature containing one or more vents. During volcanic eruptions , molten magma and volcanic gases rise from an underground magma chamber , through

345-423: The crater is situated at the top of a mountain formed from the erupted volcanic deposits such as lava flows and tephra . Volcanoes that terminate in such a summit crater are usually of a conical form. Other volcanic craters may be found on the flanks of volcanoes, and these are commonly referred to as flank craters . Some volcanic craters may fill either fully or partially with rain and/or melted snow, forming

368-412: 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

391-522: The mapping of hitherto-uncharted parts of British Columbia . In British Columbia, survey work was overseen by Walter Moberly , a former Colony of British Columbia land official and cabinet member , and involved steamboat support vessels on the Arrow Lakes and Columbia River , and on Kootenay Lake , Shuswap Lake , Seton Lake and others. The survey entailed the first detailed mapping of much of southern British Columbia, including remote areas such as

414-510: The official map, there were already several Four Mile Creeks in British Columbia, so they changed the letters to produce 'Flourmill' Creek instead. The volcanoes derive their name from the creek, and were first referred to in this way in the 1974 edition of the book, Exploring Wells Gray Park . (In 2024, British Columbia had 14 Four Mile Creeks, 2 Four Mile Lakes, and 3 Four Mile Mountains.) The first recorded visit by non-indigenous people to

437-529: The same time as Trophy Mountain was added and the Pendleton Lakes were removed from the park. Access to the Flourmill Volcanoes is by a rough road from 100 Mile House on Highway 97 . It has numerous unsigned forks and directions such as those found in Exploring Wells Gray Park are essential. The road ends at the outlet of Spanish Lake and an overgrown trail leads 3.2 km (2.0 mi) to

460-475: 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

483-503: 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 7 to 10 m (23 to 33 ft) along Spanish Creek. The lava beds extend about 15 km (9.3 mi) down

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506-446: The southwest. This lava flow averages 10 m (33 ft) thick. Both cones were built upon unweathered glacial material. Situated 2.5 km (1.6 mi) east of Spanish Lake is the northerly Spanish Lake Centre with an elevation of 1,770 m (5,810 ft). 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

529-531: The survey's activity focused on locating suitable mountain passes through the Canadian Rockies , Selkirk Mountains , Monashee Mountains , Canadian Cascades and Coast Mountains of western Canada , locating the best route across the rugged terrain of the Canadian Shield north of Lake Superior was also a primary goal. The survey played an important role in the exploration of Canada , especially in

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