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Using point and examples from the lecture, explain two ways weathering occurs.
請用課上的觀點(diǎn)和例子，解釋說明風(fēng)化發(fā)生的兩種途徑。
Listen to part of a lecture in a geology class.
請聽地理課上的部分內(nèi)容。
Rocks near the Earth's surface are directly exposed to elements in the environment such as air and water,
靠近地表的巖石直接暴露在像空氣和水這樣的環(huán)境元素中，
and also to conditions such as temperature change as well as to living organisms.
也會受到像溫度變化和生物體這樣的情況的影響。
And this exposure to the environment can actually cause even huge rocks to break into smaller pieces.
像這樣暴露在自然環(huán)境中，實(shí)際上可能會導(dǎo)致巨大的巖石碎成小塊兒。
This process is called weathering.
這個過程就叫做“風(fēng)化”。
Let's talk about a couple ways weathering occurs.
我們來講一講風(fēng)化發(fā)生的幾種途徑。
First of all, rocks are often exposed to water.
首先，巖石經(jīng)常會接觸到水。
In cold wet environments rocks can break due to water freezing inside of them.
在寒冷潮濕的環(huán)境中，巖石可能會因?yàn)閮?nèi)部的水分凍結(jié)而破裂。
How does this happen? Well, as I am sure you know, when water freezes it expands and over time this can lead to weathering.
這是如何發(fā)生的呢？我相信你們都知道，當(dāng)水結(jié)冰的時候，它的體積會膨脹，而隨著時間的推移，這就可能會導(dǎo)致風(fēng)化。
Um, imagine a rock with a small opening or crack in it. It rains and water gets into the crack and stays there.
假設(shè)有這么一塊巖石，它的表面有個小缺口或者裂縫。下雨的時候，雨水落進(jìn)了裂縫里并留了下來。
Then, at night, the temperature drops and the water inside the crack freezes.
然后到了晚上氣溫下降，裂縫里的雨水結(jié)成了冰。
This growing, expanding ice pushes outward on either side of the crack causing it to get slightly bigger.
這塊越來越大的冰從裂縫的兩邊不斷往外伸展，把裂縫變得稍微大了一些。
When this happens again and again, the crack becomes larger and eventually pieces of the rock break off.
如果這種情況反復(fù)發(fā)生，裂縫會變得越來越大，最終部分巖石就會脫落。
OK, weathering can also be caused by plants, by a plant growth.
風(fēng)化也會因?yàn)橹参锒a(chǎn)生，受到植物生長的影響。
If a plant seed gets blown into the crack of a rock, it may take roots. And its roots will grow down into the rock.
當(dāng)一粒植物種子被風(fēng)吹進(jìn)巖石的裂縫之后，它也許會在此生根。而它的根會一直往下生長穿進(jìn)巖石。
The plant's roots can cause the rock to break down, uh, fracture.
植物的根會導(dǎo)致巖石破裂。
You may have seen this with large trees growing on top of a rock, a great example of this.
你們也許見過大樹長在巖石上面，這就是個絕佳的例子，
Usually there's enough dirt in the crack of a rock or on top of a rock to allow a tree to start growing there.
一般來說，巖石的裂縫里或者巖石上方有充足的泥土可以讓一棵樹開始在那兒生長。
As the tree grows over the years, the tree's roots extend downward into the crack and crevasses of the rock in search of water and nutrients.
當(dāng)這棵樹長了幾年之后，它的根就會向下延伸進(jìn)裂縫和巖石的缺口中，尋找水分和營養(yǎng)。
Over time, the roots get bigger and grow deeper, widening and enlarging the cracks, causing the rock to break apart.
隨著時間的推移，樹根會越長越大、越長越深，不斷使裂縫變寬變大，導(dǎo)致巖石破裂。
