On the coast of Oregon is a beautiful and unique geologic oddity.
There, a more than 200 foot tall monolith of volcanic rock jets out of the ground, in
a manner somewhat similar to Devils Tower in Wyoming.
Yet, despite this feature clearly being volcanic due to the rock type it is composed of, there
are no nearby source vents which erupted volcanic material within a 20 mile radius during the
last 30 million years.
Instead, this feature and other nearby sea stacks like it originated due to one of the
planet's largest volcanic eruptions since the non avian dinosaurs went extinct which
began more than 300 miles to the east.
Haystack Rock is located in northwestern Oregon where it is 68 miles west northwest of the
city of Portland.
Haystack rock is somewhat special because it is accessible at low tide through a strip
of land but becomes inaccessible at high tide.
Looking around the adjacent beaches there a group of other basaltic rock outcroppings
and smaller monoliths, hinting at a similar origin.
In fact, these can be found via a stretch 15 miles in length along Oregon's coast.
These basaltic structures like Haystack Rock did not originate due to a submarine volcanic
eruption, but rather are a feature of the massive Columbia River flood basalts.
Around 16.7 million years ago, the top of the Yellowstone hotspot reached the crust
mantle boundary in eastern Oregon and western Idaho.
This injected massive amounts of magma into the crust, some of which erupted through incredibly
large eruptions, where lava flooded out of a lengthy fissure or group of fissures in
the Idaho Oregon border area.
During a few of these eruptions, eruptive fissures were more than 50 miles in length
and a majority of that length actively ejected molten rock.
These individual eruptions often output between 100 and more than 1,000 cubic kilometers of
lava.
This amount was unimaginably large, as for comparison, the 35 year long eruption of Kilauea
from 1983 to 2018 only produced 4.4 cubic kilometers of rock.
In other words, a single flood basalt eruption could be comparable to 227 simultaneous eruptions
of Kilauea all of which were in the far eastern section of Oregon along a narrow chain.
Over the next 1.1 million years, 93% of the more than 350 eventual eruptions which would
be generated occurred from this complex, covering large amounts of Oregon, Washington, and Idaho
in dark colored volcanic rock.
By 5.5 million years ago these eruptions had covered an area larger than the entire state
of Washington, totalling an area of around 81,000 square miles or 210,000 square kilometers.
The volume erupted was even hypothetically enough to cover the entirety of the United
States in 58 feet of volcanic rock, per the U.S. Geological Survey.
It was during this period, most likely between 16.6 and 15.6 million years ago, that one
such voluminous lava flow occurred, probably beginning in far eastern Oregon.
As lava was emitted out of a lengthy fissure at a rate of more than 10,000 cubic meters
per second, the low viscosity of the basalt lava caused it to quickly move downhill, at
a rate of several miles per hour.
After extended periods of time, lava piled up to fill valleys, causing molten rock to
be redirected towards other low points.
After several years of erupting at this incredibly high rate, the flow of molten rock reached
the Oregon coastline which was more than 300 miles to the west.
As the lava entered the ocean, it generated a series of littoral explosions.
The lava eventually covered much of the shallow seafloor, causing it to spread out as part
of a lava delta.
Lava subsequently continued to pile up to a height of several hundred feet before the
eruption ended.
In the many millions of years since, the cooled lava which would become Haystack Rock was
uplifted due to tectonic forces, and combined with persistent wave action created a series
of jagged monoliths.
Thanks for watching!
If you would like to request a specific topic, please leave a comment below!
Additionally, I would like to thank Nick B who requested this video's topic, and I wish
them a happy birthday!