火山的类型

 

What does an active volcano look like?
::活火山长什么样?

The  crater  at the summit of Mount St. Helens in the United States is an incredible  landscape . The slope is steep and the landscape is still dotted with ash and debris from an  explosive eruption  in 1980. The forest was devastated in this event, and even decades later the  ecosystem  has not fully recovered. When you're standing on the top, you can see other Cascades  : Mt. Adams, Rainier, Hood, Jefferson, and sometimes more.
::在美国,圣海伦山顶的火山口是一个令人难以置信的地貌。斜坡是陡峭的,地貌仍然充斥着1980年爆炸爆发产生的灰尘和碎片。森林在此事件中被摧毁,甚至几十年后生态系统也没有完全恢复。当你站在山顶上的时候,你可以看到其他的卡萨德斯:亚当斯山、兰尼埃山、胡德山、杰斐逊山,有时还会有更多。

Volcanoes
::火山体

A volcano is a vent through which molten   and gas escape from a  magma chamber . Volcanoes differ in many features, such as height, shape, and slope steepness. Some volcanoes are tall cones, and others are just cracks in the ground. As you might expect, the shape of a volcano is related to the composition of its  magma . The three types of volcanoes are composite,  shield , and cinder cones.
::火山是一个火山喷口,熔岩和气体从岩浆室中流出。火山在许多特征上各不相同,如高度、形状和斜坡陡峭。有些火山是高锥体,而另一些火山只是地上的裂缝。正如你可能预期的那样,火山的形状与其岩浆的构成有关。三种火山是复合的、盾牌的和煤渣的。

Composite Volcanoes
::复合火山岩

 

Figure  shows Mt. Fuji, a classic example of a  composite volcano .  Composite volcanoes  have broad bases and steep sides. These volcanoes usually have a large crater at the top. The crater was created during the volcano's last  eruption .
::图中显示了富士山,这是一座复合火山的典型例子。复合火山有广阔的底部和陡峭的两边。这些火山的顶部通常有一个大的火山口。火山口是在火山上次爆发时形成的。

Composite volcanoes are also called stratovolcanoes. This is because they are formed by alternating layers (strata) of magma and ash ( Figure ). The magma that creates composite volcanoes tends to be thick. The steep sides form because the  lava  cannot flow too far from the vent. The thick magma may also create  . Ash and  pyroclasts  erupt into the air. Much of this material falls back down near the vent. This creates the steep sides of stratovolcanoes. The composition of magma that erupts at composite volcanoes is usually  felsic  (rhyolite) or  intermediate  (andesite).
::复合火山也被称为石灰火山。 这是因为火山是由岩浆和灰( 浮石) 的交替层( 缩放层) 形成。 形成复合火山的岩浆往往很厚。 陡峭的两面会形成, 因为熔岩不会从喷口太远处流出。 厚厚的岩浆也可能产生. 灰和火化物向空气中喷发。 大部分这种物质落在喷口附近。 这造成了岩浆的陡峭两边。 在复合火山喷发的岩浆的构成通常是浮化的( 流星 ) 或中间的( 黑石 ) 。

 

Composite volcanoes are common along convergent  plate boundaries . When a tectonic  plate  subducts, it melts. This creates the thick magma needed for these eruptions. The Pacific  Ring of Fire  is dotted by composite volcanoes.
::复合火山在聚点板块边界上很常见。 当构造板块的下水道熔化时, 它会熔化。 这会产生这些火山爆发所需的厚厚岩浆。 太平洋火圈被复合火山点燃。

Shield Volcanoes
::火山盾牌

 

Shield volcanoes  look like a huge ancient warrior’s shield laid down. Pictured above is Mauna Kea Volcano ( Figure ) taken from Mauna Loa Volcano. Both volcanoes are part of the Big Island of Hawaii. A  shield volcano  has a very wide base. It is much flatter on the top than a composite volcano. The lava that creates shield volcanoes is relatively thin. The thin lava spreads out. This builds a large, flat volcano, layer by layer. The composition of lava at shield volcanoes is  mafic . Shield volcanoes are very large. For example, the Mauna Loa Volcano has a diameter of more than 112 kilometers (70 miles). The volcano forms a significant part of the island of Hawaii. The top of nearby Mauna Kea Volcano is more than ten kilometers (6 miles) from its base on the  .
::盾牌火山看起来像一个巨大的古代战士盾牌。上面的图象是Mauna Loa Volcano(Figure)从Mauna Loa Volcano拍摄的。两座火山都是夏威夷大岛的一部分。 盾牌火山的底部非常宽。 盾牌火山的顶部比复合火山要好得多。 创造盾牌火山的熔岩相对比较薄。 薄薄的熔岩会扩散。 这块熔岩会形成一个巨大的平板火山层。 盾牌火山的熔岩组成非常大。 盾牌火山非常大。 例如, Mauna Loa Volcano 的直径超过112公里( 70英里 ) 。 火山是夏威夷岛的一个重要部分。 附近的Mauna Kea Volcano 的顶部距离其基地超过10公里( 6英里 ) 。

Shield volcanoes often form along  . They also form at  hotspots , like Hawaii. Shield volcano eruptions are non-explosive.
::盾牌火山通常会形成。它们也会在夏威夷等热点形成。盾牌火山爆发是非爆炸性的。

Cinder Cones
::Cinder Connes 灰锥体

Cinder cones  are the smallest and most common type of volcano. Cinder cones have steep sides like composite volcanoes. But they are much smaller, rarely reaching even 300 meters in height. Cinder cones usually have a crater at the summit. Cinder cones are composed of small fragments of rock, called cinders. The cinders are piled on top of one another. The cinders can be mafic, intermediate, or felsic in composition. These volcanoes usually do not produce  streams  of lava. Cinder cones often form near larger volcanoes. Most composite and shield volcanoes have nearby cinder cones.
::灰鹤锥体是最小和最常见的火山类型。 灰熊锥体有像复合火山那样的陡峭的两边。 但是它们小得多, 很少达到300米高。 灰熊锥体通常在峰顶上有一个弹坑。 灰熊锥体由小块的岩石组成, 叫做灰烬。 灰熊堆在相互之间堆叠。 灰熊可能是泥浆, 中间的, 或熔岩的构成。 这些火山通常不会产生熔岩流。 火山锥体通常在更大的火山口附近形成。 大多数复合火山和盾牌火山都有附近的煤渣锥体。

Cinder cones usually build up very rapidly. They only erupt for a short time. Many only produce one eruption. For this reason, cinder cones do not reach the sizes of stratovolcanoes or shield volcanoes ( Figure ).
::灰心锥体通常会快速积聚。 它们只在短短的时间内喷发。 许多只产生一次喷发。 因此, 灰心锥体不会达到星体火山或屏蔽火山( Figure) 的大小 。

 

Summary
::摘要

• Magma composition determines both eruption type and volcano type.
  ::岩浆成分决定火山爆发类型和火山类型。

• Composite volcanoes are common at convergent boundaries. Shield volcanoes are produced at divergent plate boundaries and intraplate.
  ::复合火山在汇合边界很常见,盾牌火山在不同的板块边界和板内生产。

• Cinder cones are made of small fragments of a variety of compositions usually from a single eruption. They are found with composite and shield volcanoes.
  ::灰心锥体由各种成分的小碎片组成,通常从一次火山爆发中产生,它们与复合火山和屏蔽火山一起发现。

Review
::回顾

1. Why do mafic lavas produce shield-shaped volcanoes? Why do felsic lavas produce cone-shaped volcanoes?
   ::为什么岩浆熔岩会产生盾状火山?为什么岩浆会产生锥形火山?为什么岩浆会产生锥形火山?

1. How did composite and shield volcanoes earn their names?
   ::复合火山和盾牌火山是如何获得其名称的?

1. What features would you use to identify each of the three volcano types?
   ::你用什么特征来识别这三种火山类型中的每一种?