The nation of Portugal contains more than 20 active volcanoes, which are emplaced on
its numerous islands.
The majority of these are located within the Azores island chain, such as the Fayal volcano
which produced the chain's most recent eruption from 1957 to 1958.
However, the Azores aren't the only island of Portugal which contains a still active
volcano.
To the south is the beautiful island of Madeira, which is known for its scenery and wine.
This island is also completely volcanic in origin, and is still classified as an active
volcano.
It last erupted in 4500 BC, and is still to this day seismically active due to the deep
movement of magma in the crust.
This video will discuss this volcano and mention what its future hazards are.
The island of Madeira can be found southwest of mainland Portugal in the Atlantic Ocean,
where it is 800 kilometers west of the nation of Morocco.
Looking around the island, a number of recent volcanic features such as this young looking
lava flow can be found.
These flows are all part of a single elongated shield volcano, which is truly an impressive
size.
If you were to remove the oceans surrounding Madeira, you would realize that the volcano
towers to an impressive 6 kilometers or 19,685 feet above the ocean floor.
However, due to the presence of the ocean, less than 10% of the overall volcano is located
above sea level.
This volcano began as a submarine volcano around 6 million years ago, when magma first
erupted onto the ocean floor.
This lava originated from a low intensity underlying hotspot, not too different from
the mantle plume which led to the creation of the San Francisco volcanic field in Arizona.
As the submarine volcano continued to grow in size, two distant vents became apparent.
These vents broke the ocean's surface around 5.57 million years ago, creating two distant
islands.
Today, you can find remnants of this early period of activity at the town of Porto da
Cruz, which is built on ancient volcanic rock.
Later, the composition of rock changed from basalt to a combination of higher silica basalt
and trachyandesite.
This greater silica content caused some explosive eruptions to occur, creating vulcanian style
explosions associated with pyroclastic flows.
However, the vast majority of volcanic activity was purely effusive, which created long distance
fluid lava flows which connected the two islands.
The tallest peak of the overall island, Pico Ruivo, formed during this era of activity,
which likely represented the summit of this volcano.
More lava flows expanded the island around 2 million years ago, creating the modern western
coastline.
Afterwards, eruptions slowly became less and less frequent.
The next period of activity almost exclusively constructed medium sized vents formed by the
eruption of lava with intermittent explosions of ash called cinder cones.
Five of these can be found around the city of Funchal, which all formed in the last 1
million years.
In the last 25,000 years, volcanic activity has exclusively occurred in the center of
the island, creating lava flows on top of the Paul da Serra plateau and producing a
number of cinder cones in the adjacent valleys.
These cinder cones each produced long rivers of lava which were funneled downslope towards
the ocean.
The vent which was the site of the island's most recent eruption is unknown, but it is
located somewhere within the yellow circle shown on screen.
Several distant bombs of lava and a small ash layer have been dated to 4500 BC, so we
know that a small eruption occurred that year.
Given the long history of this beautiful volcanic island, it will erupt again.
The next eruption will almost certainly occur on either the aforementioned volcanic plateau
or the two valleys adjacent to it.
At worst, these eruptions would only be mildly explosive, ejecting bombs of lava up to 1
kilometers distant.
The main threat the Madeira island volcano poses is long distance lava flows and their
abundant gas emissions, which would force the evacuations of the nearby valleys.
With this being said, the odds of a future eruption are quite low at about 1 in 15,000
each year.
I hope that you enjoyed this video.
If you would like to request a specific topic please leave a comment below.
Additionally, if you wish to support this channel, consider becoming a patron on patreon.