Extrusive Activity Flashcards
(1) where does the cascade mountain range lie?
Along the western coast of the US extending from Northern California, through Oregon and Washington into British Columbia, Canada.
(1) what is the cascade mountain range?
A continental mountain arc formed due to the subduction of an offshore oceanic plate (Juan de Fuca) beneath the continental crust (North American plate).
(2) lava plateaux - when did the Columbia river lava plateaux form?
12-17 million years ago
(2) lava plateaux - how big is the Columbia river lava plateaux?
It is regional in scale and covers 130,000 Km squared of the states of Washington and Oregon
(2) lava plateaux - what did a fissure eruption result in?
Hundreds of separate effusive basalt flows - reach total thickness of 2000m
(2) lava plateaux - what are basalt lavas?
Very ‘runny’ and take a long time to cool
(2) lava plateaux - what is the form of volcanism in areas within plates associated with?
Mantle plumes or hot spots
(2) lava plateaux - the plateaux is…….
Very distinctive and remains stable as a landscape over time
However it is gradually denuded and sculpted by erosion from wind, rain and rivers which incise into the plateaux
(3) shield volcanoes - what are shield volcanoes made of?
Also made of fluid lava flows however unlike fissure eruptions the effusive lava erupts from a central vent, flowing in all directions.
(3) shield volcanoes - there are various shield volcanoes along the cascade range, what do these include?
Belknap,
three fingered jack,
Mount Washington,
Mount bachelor
(3) shield volcanoes - what does Belknap shield volcano and its surrounding lava flows cover?
98 sq. kilometres
(3) shield volcanoes - when did Belknaps explosive phase begin?
Over 2900 years ago
(3) shield volcanoes - Belknap is one of the cascades what?
Youngest volcanoes with lava flows as young as 1,400 years
Therefore is a dynamic landscape with potential to be rescaled in future as it receives fresh flows of lava from the central vent
(4) cinder cones - how do cinder cones form?
From the build up of pyroclastic materials ejected from a single vent
(4) cinder cones - what are cinder cones!
Explosive and geologically younger features which often from on the flanks of larger volcanoes