07. Volcano

10 interesting facts about volcano:

https://earthhow.com/facts-about-volcanoes/

Do you know that ash from volcanic eruption can sparkle lightning?

Do you know the tallest mountain on Earth is a volcano? 

Though the highest mountain above sea level is actually Mt Everest, a fold mountain.

The base of Mauna Kea is about 6000 meters below sea level and the summit is about 4000 meters above sea level. The distance between the foot of the mountain and the summit is about 10,000 meters. This makes Mauna Kea the "tallest" mountain in the world.

Will Singapore be affected by a volcanic eruption?

Refer to my post on http://olevelgeog.blogspot.sg/2014/02/impact-of-hotspots-and-volcanic.html

Where are volcanoes found? How are volcanoes formed?

These information will be handy to help you answering the inquiry question: Will Singapore be affected by a volcanic eruption?

Watch the following video on the dynamic of a volcano!

Watch the video on 6 powerful volcanic eruption, with the largest being the Krakatoa eruption in 1883.

Birth of a volcanic island

Parts of a volcano : https://earthhow.com/parts-of-a-volcano/

The map below highlight the locations of volcanoes, highlighting a concentration of volcanoes around the rim of the Pacific Plate, which is known as the Ring of Fire. This is mainly due to the subduction of the Pacific Plate, which consist of mainly denser oceanic crust below the continental crusts as it converges with the Eurasian Plate, North and South American Plates.

Most of the volcanoes are found at the convergent plate boundaries.

Oceanic-continental plate convergence

•     When an oceanic plate meets a continental plate, the denser oceanic plate subducts under the less dense continental plate.

•     A subduction zone forms, creating a deep oceanic trench along the plate boundary. 

•     The subduction of the oceanic plate causes the solid mantle material to melt and magma is formed.

•     The magma rises through the mantle and crust to emerge as lava which cools and solidifies to form volcanoes on land such as Mt Merapi in Indonesia.

Oceanic–oceanic plate convergence

• When two oceanic plates converge, one subducts under the other.

• A subduction zone forms, creating a deep oceanic trench.

• The subduction of the oceanic plate causes the solid mantle material to melt and magma is formed.

• The magma rises through the mantle and ocean floor to emerge as  lava which cools and solidifies to form volcanoes which eventually rise above the sea level to form volcanic islands such as the Mariana Islands.

Revise on how a volcano is formed @

http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/volcanoes_rev1.shtml

 Mount Agung showed signs of eruption in Sept 2017 and more than 120,000 people were evacuated.

This is the crater of Mount Agung, Bali. Look at the steeper slopes of the volcano.Other than the steam you can see pouring out of the crater, there are earthquake showing that magma is rising up to the surface and an eruption is imminent. As high as 813 earthquakes struck Mt Agung on 9 Oct 2017! 140000 were evacuated from their homes and this has seriously affected Bali economy as the area is highly dependent on tourism and many tourists have cancelled their trip to Bali in fear of their safety.

Compare the crater of Mt Agung with this picture shown in the 2017 N level paper which shows the volcanic crater on Surtsey Island in Photograph A.

• The land is barren and covered with dark volcanic soil. 

• The slope of the volcano is gentle.

• There is a depression in the middle of Photograph A which shows a possible crater. 

• There are no signs of volcanic activity so the volcano could be dormant or extinct. 

• The sea in the background indicate that this might be a volcanic island surrounded by water.

However NOT all volcanoes are formed at convergent plate boundaries. Some are formed at divergent plates boundaries.

Oceanic-oceanic plate divergence

Do take note of the process sea floor spreading in Mid-Atlantic as well when the North American plate moves away from the Eurasian plate. 

• As the North American and Eurasian plates move apart due to convection currents inside the Earth. Magma rises from the mantle to fill the gap between the plates as they diverge. 

• New sea floor is formed when the lava cools and solidifies. This process is called sea-floor spreading. 

• Magma rises at the zone of divergence/spreading zone to form a ridge of new ocean floor called mid-oceanic ridge. 

• At various points along the ridge, magma builds up above the ocean to form volcanoes. 

• Examples of such volcanoes are found where the Mid-Atlantic Ridge is found in the middle of the Atlantic Ocean cutting across Iceland, a volcanic island.

The above map shows the oceanic ridge and volcanoes at the divergent plate boundary.   The following photographs are from my sister, Catherine Teo, who visited Iceland in June 2023. 

Continental–continental plate divergence

• When the two continental plates diverge, they are stretched, causing fractures to form at the plate boundary

• The land in between the two continental plates sinks, forming a linear depression known as a rift valley

• Magma may also rises to the surface through the fractures formed due to the tension and form volcanoes near the rift valley. For example along the Great East African Rift Valley and the Red Sea.

Let's explore the volcanoes of the world - click on the kmz file at the bottom of the page or here https://wwu.instructure.com/courses/855334/files/24723522/download

You need to have Google Earth installed in order to open up the file.

Move across the continents and found out more about volcanoes around the world. Is there a certain pattern for the location of the volcano? Click on the place marker to find out more about the volcano at the location it is marked.

Visit http://volcano.si.edu/reports/usgs/  and count the number of volcanic eruptions that had taken place in the last month in different parts of the world. 

Represent it as a bar chart and classify it according to continents.

Using clues about volcanoes to find out where they are located:

http://www.classtools.net/mapgame/11_BULDZ9

You have gathered enough data on the occurrence of volcanic eruptions. Let us revisit our inquiry question:

Will Singapore be affected by a volcanic eruption?

Based on all the information gathered so far, your likely response to the inquiry question would be that Singapore is not prone to the risk of volcanic eruptions.   

Is the data collected enough to help you answer the inquiry question? 

Reflect on the activities that you completed. 

Does the data collected enable you to answer the inquiry question Will Singapore be affected by a volcanic eruption?

If not, what other information is needed for you to be able to answer the inquiry question?

Extension of learning

You have been tasked to find out more about one of the volcanoes/volcanic islands listed below:

1. Eyjafjallajökull (in Iceland)

2. Mt Fuji

3. Mt Merapi

4. Mariana  Islands

5. Mauna Loa 

6. Mt Vesuvius 

Use the 5W framework in your research and share them with the class.

Where is the volcano/volcanic islands located?

What cause the volcano/volcanic islands to be formed?

When was the last eruption?

Who are affected by the eruption?

Why do people live near to the volcano/volcanic islands?

* work by 3EV in subpage

Case study of Pinatubo

http://www.coolgeography.co.uk/GCSE/AQA/Restless%20Earth/Volcanoes/Mount%20Pinatubo.htm

This is a video clip I took at Wushan mud volcano in Kaohsiung, Taiwan. The area has been designated as a protected national park. There are also volunteer tour guide explaining the ecosystem of the area. Taiwan is located at the plate boundary which the Pacific plate converge with the Eurasian plate. Like Japan, it has many volcanoes and experiences frequent earthquakes due to tectonic plate movements.