However, the sound wasn't coming from the sky.

但那聲音聽起來不像從天空發出來的。

The source was a large, smoking crack emitting gas and ejecting rocks.

聲音的來源是一個很大、冒著煙的裂縫，正在噴出氣體和射出石頭。

This fissure would come to be known as the volcano Paricutin, and over the next 9 years, its lava and ash would cover over 200 square km.

那道深溝後來被稱為帕里庫廷火山，接著在九年內，它的岩漿和灰燼覆蓋了超過兩百平方公里的面積。

But where did this new volcano come from, and what triggered its unpredictable eruption?

但是這個新的火山是哪來的，又是什麼觸發了它不可預測的爆發？

The story of any volcano begins with magma.

任何火山故事的開頭，都得提到岩漿。

Often, this molten rock forms in areas where ocean water is able to slip into the Earth's mantle and lower the layer's melting point.

通常，在海水可以流進而把那層地函的熔點降低的地方，會形成熔融的岩石。

The resulting magma typically remains under the Earth's surface thanks to the delicate balance of three geological factors.

因為三個地理因素的微妙平衡，形成的岩漿通常會維持在地表之下。

The first is lithostatic pressure.

第一個因素是靜岩壓力。

This is the weight of the Earth's crust pushing down on the magma below.

那代表地殼的重量把岩漿往下壓。

Magma pushes back with the second factor, magmastatic pressure.

岩漿反推回來的力量是第二個因素，靜漿壓力。

The battle between these forces strains the third factor: the rock strength of the Earth's crust.

這兩股力量之間的對抗造成了第三個因素：地殼的岩石強度。

Usually, the rock is strong enough and heavy enough to keep the magma in place.

通常，岩石夠強、夠重，足以讓岩漿留在原處。

But when this equilibrium is thrown off, the consequences can be explosive.

但當這種平衡出現了偏差，後果可能會非常具有爆發性。

One of the most common causes of an eruption is an increase in magmastatic pressure.

造成火山噴發最常見的原因之一，就是靜漿壓力增加。

Magma contains various elements and compounds, many of which are dissolved in the molten rock.

岩漿包含了各種元素和化合物，當中有許多在熔岩中溶解。

At high enough concentrations, compounds like water or sulfur no longer dissolve, and instead form high-pressure gas bubbles.

濃度夠高時，像是水或硫這類化合物就不會再溶解，反而會形成高壓的氣體泡泡。

When these bubbles reach the surface, they can burst with the force of a gunshot.

當這些泡泡抵達表面時，它們爆破的力量和開槍一樣。

And when millions of bubbles explode simultaneously, the energy can send plumes of ash into the stratosphere.

當數百萬個泡泡同時爆破，產生的能量能夠將灰燼形成的羽狀煙雲送到平流層。

But before they pop, they act like bubbles of C02 in a shaken soda.

但在爆裂之前，它們就像將汽水搖動之後產生的二氧化碳泡泡。

Their presence lowers the magma's density, and increases the buoyant force pushing upward through the crust.

它們出現造成岩漿的密度下降，增加向上推向地殼的浮力。

Many geologists believe this process was behind the Paricutin eruption in Mexico.

許多地質學家相信這是墨西哥帕里庫廷火山爆發背後的過程。

There are two known natural causes for these buoyant bubbles.

這些浮力泡泡的已知天然成因有兩個。

Sometimes, new magma from deeper underground brings additional gassy compounds into the mix.

有時，在地底更深處的新岩漿會把額外的氣體化合物帶進混合物中。

But bubbles can also form when magma begins to cool.

但在岩漿開始冷卻時，也有可能形成泡泡。

In its molten state, magma is a mixture of dissolved gases and melted minerals.

在熔融狀態時，岩漿是溶解氣體與熔解礦物的混合體。

As the molten rock hardens, some of those minerals solidify into crystals.

當熔岩變硬時，一些礦物就會固化成結晶。

This process doesn't incorporate many of the dissolved gasses, resulting in a higher concentration of the compounds that form explosive bubbles.

這個過程不會用到許多溶解的氣體，導致形成爆炸性泡泡的化合物有更高的濃度。

Not all eruptions are due to rising magmastatic pressure—sometimes the weight of the rock above can become dangerously low.

並非所有的噴發都是靜漿壓力升高所造成——有時，上方岩石的重量會變得危險地低。

Landslides can remove massive quantities of rock from atop a magma chamber, dropping the lithostatic pressure and instantly triggering an eruption.

山崩有可能會帶走大量在岩漿庫上方的岩石，讓靜岩壓力下降，立刻觸發火山噴發。

This process is known as “unloading” and it's been responsible for numerous eruptions, including the sudden explosion of Mount St. Helens in 1980.

這個過程叫做「卸載」，是許多火山噴發的成因，包括 1980 年聖海倫火山的突然爆發。

But unloading can also happen over longer periods of time due to erosion or melting glaciers.

但就較長的時間來看，侵蝕或者冰河融化也有可能造成卸載。

In fact, many geologists are worried that glacial melt caused by climate change could increase volcanic activity.

事實上，許多地質學家擔心氣候變遷所造成的冰河融化有可能會增加火山活動。

Finally, eruptions can occur when the rock layer is no longer strong enough to hold back the magma below.

最後，當岩石層的強度不再足以壓住下方的岩漿時，也會發生噴發。

Acidic gases and heat escaping from magma can corrode rock through a process called hydrothermal alteration, gradually turning hard stone into soft clay.

透過一個叫做熱液蝕變的過程，從岩漿漏出的酸性氣體和熱氣就會腐蝕岩石，漸漸將堅硬的岩石轉變為軟泥土。

The rock layer could also be weakened by tectonic activity.

岩石層也有可能因為板塊活動而變弱。

Earthquakes can create fissures allowing magma to escape to the surface, and the Earth's crust can be stretched thin as continental plates shift away from each other.

地震可能會造成裂縫，讓岩漿能滲出地表，且當板塊彼此遠離時，地殼就可能因被拉伸而變薄。

Unfortunately, knowing what causes eruptions doesn't make them easy to predict.

不幸的是，知道噴發的成因並不能協助預測噴發。

While scientists can roughly determine the strength and weight of the Earth's crust, the depth and heat of magma chambers makes measuring changes in magmastatic pressure very difficult.

雖然科學家可以大略判斷出地殼的強度和重量，岩漿庫的深度和熱度讓測量靜漿壓力變化非常困難。

But volcanologists are constantly exploring new technology to conquer this rocky terrain.

但，火山學家經常在探索新技術來克服這多岩的地形。

Advances in thermal imaging have allowed scientists to detect subterranean hotspots.

熱成像的進步讓科學家可以偵測出地下的熱點。

Spectrometers can analyze gases escaping magma.

光譜儀可以分析從岩漿漏出的氣體。

And lasers can precisely track the impact of rising magma on a volcano's shape.

雷射可以精準追蹤岩漿上升對於火山形狀的影響。

Hopefully, these tools will help us better understand these volatile vents and their explosive eruptions.

希望這些工具能協助我們更了解這些不穩定的噴發口，以及它們的爆發性噴發。