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Tectonic Hazards
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Volcanology (GCSE)
In this course, Professor David Pyle (University of Oxford) introduces the topic of volcanoes. We begin by: (i) thinking about the different types of tectonic hazards; (ii) the global distribution and characteristics of volcanoes; (iii) the structure and formation of stratovolcanoes; and (iv) shield volcanoes; (v) the positive and negative effects of living with volcanoes; (vi) how we monitor and research volcanoes; (vii) a case study of a volcanic eruption, the 2021 eruption of Mount Nyiragongo in the D.R.C.; before finally (viii) a case study of a volcanic eruption on La Palma, Canary Islands in 2021.
Tectonic Hazards
In this lecture, we explore natural hazards with a focus on tectonic and geophysical hazards such as earthquakes and volcanic eruptions. We explain how these hazards are linked to the movements of the Earth’s plates, illustrating their impacts with recent examples like the large earthquakes in Türkiye in 2023, and the catastrophic 2011 Tōhoku earthquake in Japan. To finish off, we also show how volcanism is possible at tectonic boundaries.
I'm David Pyle.
00:00:06I'm a volcanologist and a professor of Earth Sciences at
00:00:07the University of Oxford.
00:00:10I've travelled around the world studying volcanoes,
00:00:12and today I'm going to be talking about natural hazards,
00:00:15and then volcanoes and the hazards associated with
00:00:19volcanic activity.
00:00:21So natural hazards are important because they pose
00:00:24risks to people and to property.
00:00:27Natural hazard events usually significant events,
00:00:30which cause loss of life, extreme damage to property, infrastructure,
00:00:34or otherwise disrupt the patterns of human behaviour.
00:00:40The focus today is on tectonic hazards or geophysical hazards.
00:00:45So these are hazards that are associated with,
00:00:50movements within the crust, for example,
00:00:53the breaking of rock causing earthquakes,
00:00:55or with the movement of magma towards the surface,
00:00:58molten rock, which then might erupt in volcanic eruptions.
00:01:01What scientists what scientists have known for for many years
00:01:06is that that the distribution of large earthquakes and
00:01:09volcanic eruptions are not uniform everywhere on
00:01:13the surface of the earth.
00:01:17So this observation,
00:01:19which people made in the eighteen hundreds,
00:01:21culminated in the idea of plate tectonics.
00:01:23And, in plate tectonic theory,
00:01:27we can imagine that the surface of the earth,
00:01:29the outer brittle part of the earth,
00:01:31is actually broken up into plates that are more or less
00:01:33rigid and there are about seven large plates and eight smaller plates.
00:01:37And most of the tectonic features that we see at the
00:01:43surface of the Earth are related to the movement of
00:01:46the plates, sometimes where the plates move side by side,
00:01:50sometimes where one plate is sinking beneath another,
00:01:54and in other places where the plates are pulling apart.
00:01:57So, tectonic hazards, geophysical hazards,
00:02:01are often associated with moments when the boundaries of
00:02:04plates, two plates, get stuck together,
00:02:08but the rest of the plates trying to move,
00:02:12because it's moving across the surface of the interior.
00:02:15And eventually the strain builds up to such an extent
00:02:19that the boundary snaps, some rocks break and you get a large earthquake.
00:02:24We see dramatic examples of this every year.
00:02:30In recent years, for example,
00:02:33we saw a very large sequence of earthquakes in Turkey
00:02:34where a stretch of the Earth's crust,
00:02:37a few hundred kilometres long,
00:02:42moved by between eight and ten metres in the in the space of
00:02:44two very large earthquakes.
00:02:48There are different places on earth which are more or less,
00:02:51likely to feel the effects of large earthquakes and volcanic eruptions.
00:02:56And, mostly, these locations are associated with plate boundaries,
00:03:02or boundaries where the plates are trying to move past each
00:03:06other, under each other or over each other.
00:03:09But, in fact, you can find that there are smaller earthquakes in many
00:03:13places across the globe, and those are related to local
00:03:18effects within the crust.
00:03:22And you can also find in some parts of the world there are
00:03:24volcanic eruptions that are not necessarily associated with
00:03:28plate boundaries.
00:03:31The hazards associated with earthquakes and volcanic
00:03:33eruptions might also include,
00:03:38things like landslides,
00:03:42avalanches.
00:03:44And it's not unusual when you have a very large natural
00:03:46hazard event, that the first event,
00:03:51let's say a very large earthquake,
00:03:53might then trigger a cascade of hazards.
00:03:55So a large earthquake
00:03:58destabilises
00:04:01landmasses,
00:04:03might well then be followed by landslides.
00:04:04The next time it rains, then there might well be,
00:04:07mudflows and so on.
00:04:10So an example of a a series of coupled
00:04:14tectonic hazards was the twenty eleven Tohoku earthquake off
00:04:17Japan.
00:04:23This was an extraordinarily large earthquake.
00:04:24It rated a magnitude nine on the Ricola scale.
00:04:27And the earthquake was caused by large scale plate movement
00:04:31as the Pacific Plate slipped dramatically underneath
00:04:35Japan.
00:04:39It had been stuck for a long time geologically and then it moved.
00:04:40The large scale movement of the seafloor
00:04:45triggered a tsunami.
00:04:47So the earthquake itself,
00:04:49the effects of the earthquake were felt first.
00:04:52The tsunami was then triggered.
00:04:54That washed very rapidly up onto the shore of Japan.
00:04:57And over the next few hours the Tsunami wave propagated,
00:05:00travelled across the Pacific Ocean, it reached Hawaii,
00:05:04California and eventually reached Antarctica.
00:05:08Following the Tohoku earthquake,
00:05:12we realized that, in fact, the engineering structure,
00:05:15the structures that that people had built in order to protect
00:05:19against the effects of tsunami,
00:05:22hadn't taken account fully of the way that the land surface
00:05:24could actually move during a large earthquake.
00:05:28So large areas were inundated by seawater,
00:05:31which were not expected from the original design of the sea defenses.
00:05:36One of the most extraordinary examples of economic impacts following the,
00:05:43the Tohoku earthquake was the fact that there was then
00:05:49a critical disaster at a nuclear power station.
00:05:53While that was not expected,
00:05:58it gives you an idea of the challenges of dealing with
00:06:00extreme natural events,
00:06:03is that sometimes those events can be so large
00:06:05that the rare scenarios that we've ignored
00:06:09when we've thought about what might happen next actually turn
00:06:13out to be, true.
00:06:16
Cite this Lecture
APA style
Pyle, D. (2024, May 24). Volcanology (GCSE) - Tectonic Hazards [Video]. MASSOLIT. https://massolit.io/courses/volcanology-gcse/case-study-la-palma
MLA style
Pyle, D. "Volcanology (GCSE) – Tectonic Hazards." MASSOLIT, uploaded by MASSOLIT, 24 May 2024, https://massolit.io/courses/volcanology-gcse/case-study-la-palma