[新聞] 加州深層地殼正在發生不可逆的分層剝離

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1.媒體來源:

外媒    sciencealert

2.記者署名:

Mike McRae

3.完整新聞標題:

Earth's Crust May Be Peeling Away Deep Beneath California

加州深層地殼正在發生不可逆的分層剝離

4.完整新聞內文:

Earth's Crust May Be Peeling Away Deep Beneath California
Nature
28 January 2025
ByMike McRae

Earth's Crust May Be Peeling Away Deep Beneath California's Sierra Nevadas
Yosemite at dawn in the Sierra Nevadas, California. (bluejayphoto/Getty
Images)

Like a moth in a cocoon, the metamorphosis of Earth's crust from molten goop
to solid land is hidden from view, leaving scientists to guess at how the
eons-long process unfolds.

黎明時分，加州內華達山脈的優勝美地。 （青鳥照片/蓋蒂圖片社）

就像繭中的飛蛾一樣，地殼從熔化的黏稠物到固體陸地的變質過程被隱藏在視線之外，讓
科學家猜測這個漫長的過程是如何展開的。

Using nearly four decades of seismic data from stations encompassing the
northern, central, and southern Sierra Nevada along California's eastern
border, geologists have uncovered signs of a critical separation between the
cool continental crust and mantle below.

利用加州東部邊界內華達山脈北部、中部和南部各站近四十年的地震數據，地質學家發現
了涼爽的大陸地殼和地函之間存在嚴重分離的跡象。

The findings – made by researchers Vera Schulte‐Pelkum from the University
of Colorado Boulder and Deborah Kilb from the University of California San
Diego – help resolve a perplexing mystery on how our planet generates the
lighter portions of its crust from the dense mix of minerals churning beneath.

Thanks to their relatively higher proportions of minerals that include
silicates, aluminium, and potassium, the chunks of rock we live upon
typically rise a touch higher than the submerged chunks of oceanic crust,
which by comparison tends to be richer in heavier elements like iron and
magnesium.

科羅拉多大學博爾德分校的研究人員維拉·舒爾特-佩爾庫姆和加州大學聖地亞哥分校的
黛博拉·基爾布的研究結果有助於解決一個令人費解的謎團，即我們的星球如何從密集的
礦物攪拌中產生地殼的較輕部分下方。

由於矽酸鹽、鋁和鉀等礦物質的比例相對較高，我們賴以生存的岩石塊通常會比海洋地殼
的水下塊高出一點點，相比之下，海洋地殼往往富含鐵和鉀等重元素。

How these materials form, and why they're so different, is an ongoing
question that researchers are slowly piecing together. The heavier elements
in oceanic crust are part of the basaltic recipe found in the upper mantle,
implying the makeup of the continental crust could be the result of denser
components separating out of the mix.

One means by which this could happen involves the dense basalt melting while
wet and under great pressure, allowing its minerals to separate into
relatively distinct sheets. Being so heavy, the lower layer might then 'peel'
free to slowly sink into the circulating currents of molten rock making up
the rest of the mantle.

這些材料是如何形成的，以及為何它們如此不同，是一個持續存在的問題，研究人員正在
慢慢拼湊起來。洋殼中較重的元素是上地函中發現的玄武岩成分的一部分，這意味著大陸
地殼的組成可能是從混合物中分離出較緻密成分的結果。

發生這種情況的一種方法是緻密的玄武岩在潮濕和高壓下熔化，使其礦物分離成相對不同
的片狀。由於如此沉重，下層可能會“剝離”，慢慢地沉入構成地函其餘部分的熔岩循環
流中。

It's an appealing hypothesis in need of solid evidence, so Schulte‐Pelkum
and Kilb went hunting for signs in a location some suspected was steadily
being stripped of its heavy igneous roots.

The Sierra Nevada is in a seismically active region of the western US,
allowing researchers to use the speed and reflection of waves rippling from
constant tiny tremors to 'map' the depths beneath the mountain range.

這是一個需要確鑿證據的吸引人的假設，因此舒爾特-佩爾庫姆和基爾佈在一些人懷疑其
沉重的火成樹根正在逐漸被剝離的地方尋找跡象。

內華達山脈位於美國西部的地震活躍地區，研究人員可以利用持續微小震動產生的波的速
度和反射來「繪製」山脈下方的深度。

Signals from these ripples, along with examples of mineral fragments of one
sort enveloped within rocks of another were already convincing some
geologists that the region had experienced delamination (separation of
layers) in the past.

Unfortunately the same clues could be interpreted as remnants of a long
buried slab of crust, demanding additional readings to clarify the region's
seismic anomalies.

Comparisons between seismic datasets representing different depths between
the Sierra Nevada confirmed a vast shear zone under the southern and central
areas at depths close to the mantle boundary. This zone becomes increasingly
distinct towards the mountain range's south.

來自這些漣漪的訊號，以及一種礦物碎片包裹在另一種岩石中的例子已經讓一些地質學家
相信，該地區過去曾經歷過分層（層分離）。

不幸的是，同樣的線索可能被解釋為長期埋藏的地殼板的殘餘物，需要額外的讀數來澄清
該地區的地震異常。

代表內華達山脈不同深度的地震資料集之間的比較證實了南部和中部地區在接近地函邊界
的深度處存在巨大的剪切帶。該區域向山脈南部變得越來越明顯。

https://imgur.com/5T1bSHE.jpg

shear zone under sierra nevada, diagram

Perspective view of imaged shear layer in the central and southern Sierra,
with a map of the ground above and a layout described by seismic data of the
separation deep below. (Schulte‐Pelkum & Kilb, Geophysical Research Letters,
2024)

"The sense of shear is consistent with west‐ to southwestward removal of
lithosphere," the researchers write in their paper, confirming theories the
heavy base of California's crust has been sinking over millions of years,
tearing itself free over a span of hundreds of kilometers in a process that 
could be mirrored in similar chunks of continent all over the globe.

中部和南部山脈的成像剪切層透視圖，上面是地面地圖，下面是由地震資料描述的佈局
。 （Schulte‐Pelkum & Kilb，地球物理研究快報，2024 年）

研究人員在論文中寫道： 「剪切力的感覺與岩石圈從西向西南方向的移動相一致。」這
證實了加州地殼的沉重底部在數百萬年裡一直下沉的理論，在數百公里的地理跨度上將
自身撕裂。

What we see above the surface – from the rise and fall of mountains to the
sinking of vast basins to the emergence of entire continents – is mirrored
by a complex shearing, dripping, melting, and wearing out of sight tens or
even hundreds of kilometers below the surface.

If we listen in just the right way, however, we can hear the skin of our
planet softly stir as it ever so slowly changes.

This research was published in Geophysical Research Letters.

我們在地表上看到的一切—從山脈的起伏到巨大盆地的下沉，再到整個大陸的出現—
都反映在數十甚至數百公里以下看不見的複雜剪切、滴落、融化和磨損中。

然而，如果我們以正確的方式聆聽，我們可以聽到地球的表面在緩慢變化時輕輕攪拌。

這項研究發表在《地球物理研究快報》。

5.完整新聞連結 (或短網址)不可用YAHOO、LINE、MSN等轉載媒體:

https://reurl.cc/96qvG8

6.備註:

果然在打聖杯戰爭，打到地殼都快被黑泥吞掉了...


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→ cuteSquirrel: 這部有看過 加州大地震
推 BLACKLIONS: 加州大乳搖
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推 fzrpower: 加州要脫包轉大人了...
推 mkopin: 要獨立了
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推 HodorDragon: 加州大乳搖
→ aids893001: 還有幾集可以逃
→ aa9012: 地震元年？
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推 WWIII: 搖死這群民主黨的
推 NSRC: 　　　　　　　　大加州地震
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