糟糕的標誌

當一位地質學家帶著記號筆遇到公共標誌上的錯誤資訊時,會發生什麼?

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本文發表於《大眾科學》的前部落格網路,僅反映作者的觀點,不一定代表《大眾科學》的觀點


夏季探險季即將到來,這意味著您可能很快會聽到地質學家在參觀具有地質意義的公共景點時發出的痛苦呻吟。您看,問題就出在那些資訊標誌上。其中一些標誌資訊量很大——只是它們不完全準確。有時更恰當地說,它們是誤導性的。這往往會讓地質旅行者感到沮喪:反應可能包括呻吟、抱怨和翻白眼。一位在俄勒岡州夏日湖嚴重不滿的地球科學愛好者親自採取行動(並帶著記號筆),進行了一些糾正性的實地考察

Image shows a portion of an information sign. To the left is printed matter reading, "Summer Lake was formed by tectonic forces that pushed and twisted this landscape into ridges and valleys over the past ten million years. Winter Ridge, rising to the west of the lake, is Summer Lake's "fault scarp." Millions of years ago, the bedrock of the ridge and the bedrock underlying the lake were pushed together (this is struck through and "pulled apart is written above in black Sharpie). The lakebed sank, and the bedrock split along a north-south fault line, and Winter Ridge rose, forming a steep slope - a scarp - between the two faults." To the right is a diagram of the area with arrows showing the movement of the fault. The arrows clearly show that the two sides pulled in opposite directions, and the center dropped down.
夏日湖的資訊標誌,顯示了讓這位精通地質知識的遊客如此痛苦的部分。圖片來源:達娜·亨特
 

嘿,至少插圖大致是正確的!


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儘管有誤導性的標誌,夏日湖仍然是一個地質學上非常迷人的地方。您可能需要帶一支記號筆,以防需要重新整理更正。

您始終需要以批判的眼光閱讀這些標誌。官員們盡力而為,但通常情況下,這些標誌並沒有經過了解安裝區域地質情況的人員的審查。而且更換它們的成本可能很高,因此對於資金緊張的實體來說,糾正它們可能不是優先事項。因此,如果您想了解您所看到的事物背後的準確故事,請儘量獲取由地球科學家或知道如何進行研究的作家編寫的指南。

有時,您會去到一些沒有指南的美麗的當地公園,但那裡確實有一些有問題的標誌。以西雅圖附近的欺騙瀑布為例。這是一個非常美麗的地方,到處都是莊嚴的樹林和奔騰的河流,還有幾個令人驚歎的瀑布。其中最令人印象深刻的是泰伊河在堅硬的岩石中轉了 90° 角的瀑布。

Image shows a waterfall plunging from the right, into whitewater just below. The river flows on along a narrow, straight channel perpendicular to the falls. Dark gray rock and deep green trees rise around it.
泰伊河從壯觀的瀑布傾瀉而下,形成更加壯觀的直角轉彎。圖片來源:達娜·亨特
 

令人驚歎,不是嗎?它只是在引誘您去找出到底是什麼原因造成了如此奇異的自然特徵。我的意思是,河流可能非常曲折,但它們通常不會以直角移動!

這已經足夠奇怪了,以至於值得花費大量精力來建造觀景臺並安裝標誌。

Image shows a sign mounted on the overlook rail at the Tye River. It asks, "Which Way to Flow?" An illustration of a bit of the river occupies the middle. Around it, blurbs say, "Why does the Tye River suddenly turn right in the stretch of river below you? It almost looks as if a thirsty giant bent the channel like a drinking straw. The river probably once ran straight. If you explore the area where it might have flowed, you find an abandoned streambed. Meager rivulets seem from rock cracks, dribbling into a dark, stagnant pool where a waterfall once plunged." To the right are three illustrations and some speculations that will be described in the next photo.
泰伊河的標誌。左側沒問題。右側不對。圖片來源:達娜·亨特
 

這個標誌盡力提供幫助,值得稱讚,但其中一個推斷是完全不可能的。

Image shows three line drawings with speculations beside them. The first shows a pile of logs stuck in the rocks along the river. Beside it is the first speculation: "No one knows for sure why the river turns. 1. Was the river diverted by the massive stack of logs piled during a flood?" The second illustration is a line drawing of the current falls and course of the river, showing the right-angle turn through granitic rock with mafic dikes. The caption beside it says, "2. Could the water be following a layer of soft rock that runs at right angles to the stream's original course?" The third illustration is a line drawing showing the old channel, the current channel leading to the old one, and the current channel that goes off at a right angle. The illustration shows a rubbly layer in the rock opposite the bend that says "Fault-damaged rock layer." The caption beside it says, "3. Does the stream turn right to flow along a fault line? Fault rocks erode easily since they are cracked and damaged when the earth moves."
其中一件事是不可能發生的。圖片來源:達娜·亨特
 

您能分辨出哪一個是絕對不可能的嗎?

如果我告訴您我們正在處理的是哪種岩石,也許會有所幫助。這些是喀斯喀特山脈堅硬的火成岩。它們大多是巨大的花崗岩岩基,但其中貫穿著安山岩岩脈。在許多地方,流動的水已經將這些岩石磨平,顯示出它們的強度,以及安山岩與花崗岩的無縫融合。

確實是一個充滿斷層線的區域——當山脈被近海的俯衝帶向上推時,山脈的骨骼會斷裂和呻吟。而被斷層削弱的岩石更容易被水侵蝕。

但是,如果有人碰巧帶著記號筆去那裡進行更正,我會鼓勵他們選擇選項 2。絕對劃掉 #1:河流不可能在木頭腐爛之前切穿那塊堅硬的岩石。而且,雖然有很多斷層,並且 #3 是一種明顯的可能性,但我會押注河流侵蝕了岩脈。在該區域的許多地方,顯然有河流侵蝕岩脈的跡象,而沒有太多證據表明存在筆直的斷層線貫穿。

我想三分之二還不錯,是吧?

當您今年夏天進行戶外探險時,請留意您遇到的資訊標誌上的明顯錯誤。而且,如果您願意,您可以與我分享!我將在下面保持評論開放。

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