火山

What causes volcanoes to erupt?

::火山喷发的原因是什么？

A volcano can look like it would do little harm. They can stay silent, or dormant, for a long time. You never know when they may wake up. Knowing when they will erupt is very important. Do you know why?

::火山可能看起来不会造成什么危害。它们可以长时间保持沉默或休眠。你永远不知道他们什么时候会醒来。知道它们何时会爆发是非常重要的。你知道为什么吗？

Many people live near a volcano. Volcanoes can cause a lot of damage. That is why we need to learn about them. Scientists study them to keep us safe.

::许多人住在火山附近。火山会造成很大的破坏。这就是为什么我们需要了解他们。科学家研究它们是为了保护我们的安全。

Some volcanoes are very active. They erupt a lot. A volcano in Hawaii is like that. It has erupted for three decades. It never explodes like some others. It just belches out lava. The lava comes out slow and thick. The lava moves very slowly. You can walk faster than the lava. Why is it helpful to know its speed?

::有些火山非常活跃。它们经常爆发。夏威夷的火山就是这样。它已经喷发了30年。它从不像其他的那样爆炸。它只是喷出熔岩。熔岩缓慢而厚实地涌出。熔岩移动非常缓慢。你可以走得比熔岩还快。为什么知道它的速度是有帮助的？

Some volcanoes may sit quiet for a long time. One day they just suddenly erupt. Quick events like these can cause many problems. If people are not aware, they cannot prepare. They must be ready to move to safety.

These fast eruptions can drop a lot of ash onto an area. Ash is very fine. It is about the size of sand. It can bury homes and cars. The hot lava can start fires. The blast can even knock down trees.

::有些火山可能静默很长一段时间。有一天它们突然爆发了。像这样的快速事件可能会导致许多问题。如果人们没有意识到，他们就无法做好准备。他们必须准备好转移到安全的地方。这些快速的喷发会使大量的火山灰落在一个地区。灰很细。它和沙子差不多大。它可以掩埋房屋和汽车。炽热的熔岩会引发火灾。爆炸甚至可以吹倒树木。

The pressure builds inside the volcano. This happens over many years. This is what happened at Mt. St. Helens. It sat quiet for 150 years. All the while, the pressure built up. In 1980, changes could be seen and felt. There were small earthquakes. A bulge was seen on the mountain. Why do you think these changes were important to notice?

::火山内部的压力越来越大。这种情况持续了很多年。这就是发生在圣海伦斯山的事情。它安静地坐了150年。与此同时，压力越来越大。1980年，人们可以看到和感受到变化。有小地震。在山上可以看到一个凸起。为什么你认为这些变化很重要？

Some scientists want to learn more about volcanoes. They study how often a volcano may erupt. They want to know what to expect. People depend on what they learn. Why is it important to learn about volcanoes?

::一些科学家想更多地了解火山。他们研究火山爆发的频率。他们想知道接下来会发生什么。人们依赖于他们学到的东西。为什么了解火山很重要？