Monday, April 5, 2010

Yellowstone National Park (9-10)


[1. 簡介] [2. 旅遊建議/食宿交通] [3. Sightseeing] [4. Winter Activities] [5. Wildlife Watching] [6. Day Hiking] [7. Other Activities] [8. Who's Who in the Park] [9. More about the Park] [10. 感想]


9. More about the Park

[9-1. Geysers around the World] [9-2. How Geysers Work?] [9-3. Wolves: A Legend Returns to Yellowstone] [9-4. Yellowstone Cutthroat Trout] [9-5. Yellowstone Fires of 1988] [9-6. Supervolcano under Yellowstone: It's Overdue] [9-7. Early Expedition/Survey in Yellowstone] [9-8. Greater Yellowstone Ecosystem] [9-9. Thermophiles] [9-10. Geyserite vs Travertine] [9-11. Lodgepole Pine] [9-12. US Army/Fort Yellowstone] [9-13. Namesake of Yellowstone] [9-14. Yellowstone Trivias] [9-15. Winter Use Plan] [9-16. Superintendent's Talk] [9-17. Book: Winter Wonderland in Yellowstone]

9-10. Geyserite vs Travertine

這算是地質小教室,主要是這黃石公園地熱區的堆積物有兩種類別,分別是geyserite與travertine。

首先是geyserite,主要出現在有geyser存在的地熱區,這種地方地底的熱水旁岩石結構屬於rhyolite(流紋岩),是含二氧化矽量相當高的火山岩,因此地底的熱水裡有相當高的二氧化矽(silica)溶解在裡面,當geyser噴出水或是水從hot springs溢出時,這些二氧化矽冷卻下來,因此形成了geyserite(hydrous silicon dioxide)這東西。

IMG_3131
Figure 9-10.1: 這是對geyserite的解釋,很多geyser的cone或是噴口旁的堆積物形成的紋路,就是這東西造成的。

IMG_3132
Figure 9-10.2: 另一種堆積物叫做travertine,主要是在Mammoth Hot Springs那一區,本質上跟鐘乳石洞的石筍(stalagmite)與鐘乳石(stalactite)類似。

Travertine是Mammoth Hot Springs那堆梯田形成的原因,而travertine形成的方式跟geyserite類似,只不過沈積物的主要成分是碳酸鈣(calcium carbonate)而不是二氧化矽(silica),之所以是碳酸鈣的原因是熱水所在的環境是limestone(石灰岩)而不是rhyoliye(流紋岩)。也就是說,travertine跟大部分石灰岩洞穴或是鐘乳石洞穴看到的結構類似,差別是在洞穴裡水常常由上往下滴,所以通常形成石筍(stalagmite)與鐘乳石(stalactite)這種結構,但地熱區水常常是由上往下流,所以常常是travertine terrace這種結構。

這種travertine是很流行的建材,且在很久以前就被拿去用,比如約二千年前的古羅馬競技場(Colosseum),就是用這東西蓋的。而一些歐洲的城堡甚至是現代的建築物,也常用travertine當建材蓋成牆壁。不過黃石公園的travertine是只供觀賞,不能拿去做商業用途就是。

IMG_6421 Castle Geyser, Yellowstone National Park
Figure 9-10.3: Castle Geyser的cone與旁邊的紋路很醒目,主要成分就是geyserite。

IMG_6105 Travertine Terrace in Mammoth Hot Springs, Yellowstone National Park
Figure 9-10.4: Mammoth Hot Springs的梯田的就是travertine構成的,也就是travertine terrace。

IMG_7698 Main Terrace, Yellowstone National Park
Figure 9-10.5: 另一個在Mammoth Hot Springs看到因travertine形成的結構,鐘乳石洞穴也可以看到類似的,因為形成的方式與成分類似。

這種travertine是很流行的建材,且在很久以前就被拿去當建材,比如約二千年前的古羅馬競技場(Colosseum),就是用這東西蓋的。而一些歐洲的城堡甚至是現代的建築物,也常用travertine當建材蓋成牆壁。不過黃石公園的travertine是只供觀賞,不能拿去做商業用途就是。

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[9-1. Geysers around the World] [9-2. How Geysers Work?] [9-3. Wolves: A Legend Returns to Yellowstone] [9-4. Yellowstone Cutthroat Trout] [9-5. Yellowstone Fires of 1988] [9-6. Supervolcano under Yellowstone: It's Overdue] [9-7. Early Expedition/Survey in Yellowstone] [9-8. Greater Yellowstone Ecosystem] [9-9. Thermophiles] [9-10. Geyserite vs Travertine] [9-11. Lodgepole Pine] [9-12. US Army/Fort Yellowstone] [9-13. Namesake of Yellowstone] [9-14. Yellowstone Trivias] [9-15. Winter Use Plan] [9-16. Superintendent's Talk] [9-17. Book: Winter Wonderland in Yellowstone]

[1. 簡介] [2. 旅遊建議/食宿交通] [3. Sightseeing] [4. Winter Activities] [5. Wildlife Watching] [6. Day Hiking] [7. Other Activities] [8. Who's Who in the Park] [9. More about the Park] [10. 感想]

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