Natural Disasters — Important Questions

Amount of gases and vapour versus the width of the vent — more gas with narrow vent causes dangerous eruption

Step 1: The chapter clearly explains that the danger level of a volcanic eruption depends on two factors working together. Step 2: If the amount of gases and vapour is more AND the vent (opening) on the Earth's surface is narrow, then the eruption is dangerous and explosive. This is because a lot of pressure builds up but has only a small opening to escape through, causing a violent explosion. Step 3: On the other hand, if the amount of gases is less AND the vent is broad and wide, then the molten lava comes out slowly and spreads itself gently on the Earth's surface. Step 4: This is similar t

The potassium-rich soil from volcanic residuals helps farmers obtain abundant crop production

Step 1: Although volcanoes cause destruction, the chapter mentions several benefits of volcanic activity. Step 2: One major benefit is that lava increases the fertility of land. The soil formed from volcanic material is extremely rich in minerals, especially potassium. Step 3: The chapter specifically mentions Java and Sumatra as examples — these islands have very good agricultural production because their soil is made of lava and is very fertile. The potassium-rich volcanic soil helps farmers get abundant crops. Step 4: Additionally, the chapter mentions other benefits: hot water springs with

Lapilli — they are useful because they can be moulded easily

Step 1: The chapter specifically mentions small rocks thrown out during volcanic eruptions by name. Step 2: These small rocks are called 'Lapilli'. This is an important vocabulary term from the chapter. Step 3: The chapter states that Lapilli have proven to be very useful because they can be moulded easily. This makes them valuable as a building or crafting material. Step 4: Option A is incorrect because magma is the molten rock inside the Earth before it reaches the surface, not a small rock thrown out during eruption. Also, magma does not contain large amounts of gold and silver as described

700 to 1600 kilometres

Step 1: The chapter provides a specific measurement for tsunami wave length. It states that the length of tsunami waves is approximately 700 to 1600 kilometres. Step 2: This enormous length is what makes tsunamis so different from ordinary ocean waves. Regular sea waves might be a few metres long, but tsunami waves stretch for hundreds of kilometres. Step 3: This great length, combined with great speed and force, is what gives tsunamis their destructive power when they reach the coastline. Step 4: Options A and B give lengths that are far too small — these would be closer to large storm waves,