糟糕的标志

当一位地质学家带着记号笔遇到公共标志上的错误信息时,会发生什么?

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本文发表于《大众科学》的前博客网络,仅反映作者的观点,不一定代表《大众科学》的观点


夏季探险季即将到来,这意味着您可能很快会听到地质学家在参观具有地质意义的公共景点时发出的痛苦呻吟。您看,问题就出在那些信息标志上。其中一些标志信息量很大——只是它们不完全准确。有时更恰当地说,它们是误导性的。这往往会让地质旅行者感到沮丧:反应可能包括呻吟、抱怨和翻白眼。一位在俄勒冈州夏日湖严重不满的地球科学爱好者亲自采取行动(并带着记号笔),进行了一些纠正性的实地考察

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.
夏日湖的信息标志,显示了让这位精通地质知识的游客如此痛苦的部分。图片来源:达娜·亨特
 

嘿,至少插图大致是正确的!


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尽管有误导性的标志,夏日湖仍然是一个地质学上非常迷人的地方。您可能需要带一支记号笔,以防需要刷新更正。

您始终需要以批判的眼光阅读这些标志。官员们尽力而为,但通常情况下,这些标志并没有经过了解安装区域地质情况的人员的审查。而且更换它们的成本可能很高,因此对于资金紧张的实体来说,纠正它们可能不是优先事项。因此,如果您想了解您所看到的事物背后的准确故事,请尽量获取由地球科学家或知道如何进行研究的作家编写的指南。

有时,您会去到一些没有指南的美丽的当地公园,但那里确实有一些有问题的标志。以西雅图附近的欺骗瀑布为例。这是一个非常美丽的地方,到处都是庄严的树林和奔腾的河流,还有几个令人惊叹的瀑布。其中最令人印象深刻的是泰伊河在坚硬的岩石中转了 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.
泰伊河从壮观的瀑布倾泻而下,形成更加壮观的直角转弯。图片来源:达娜·亨特
 

令人惊叹,不是吗?它只是在引诱您去找出到底是什么原因造成了如此奇异的自然特征。我的意思是,河流可能非常曲折,但它们通常不会以直角移动!

这已经足够奇怪了,以至于值得花费大量精力来建造观景台并安装标志。

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.
泰伊河的标志。左侧没问题。右侧不对。图片来源:达娜·亨特
 

这个标志尽力提供帮助,值得称赞,但其中一个推断是完全不可能的。

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发生的。图片来源:达娜·亨特
 

您能分辨出哪一个是绝对不可能的吗?

如果我告诉您我们正在处理的是哪种岩石,也许会有所帮助。这些是喀斯喀特山脉坚硬的火成岩。它们大多是巨大的花岗岩岩基,但其中贯穿着安山岩岩脉。在许多地方,流动的水已经将这些岩石磨平,显示出它们的强度,以及安山岩与花岗岩的无缝融合。

确实是一个充满断层线的区域——当山脉被近海的俯冲带向上推时,山脉的骨骼会断裂和呻吟。而被断层削弱的岩石更容易被水侵蚀。

但是,如果有人碰巧带着记号笔去那里进行更正,我会鼓励他们选择选项 2。绝对划掉 #1:河流不可能在木头腐烂之前切穿那块坚硬的岩石。而且,虽然有很多断层,并且 #3 是一种明显的可能性,但我会押注河流侵蚀了岩脉。在该区域的许多地方,显然有河流侵蚀岩脉的迹象,而没有太多证据表明存在笔直的断层线贯穿。

我想三分之二还不错,是吧?

当您今年夏天进行户外探险时,请留意您遇到的信息标志上的明显错误。而且,如果您愿意,您可以与我分享!我将在下面保持评论开放。

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