By Crispin Savage
呈現出陸地如何拚合的新模型對於地球歷史提供了全新觀點，也有助於我們更加瞭解地震與火山這類自然災害。
新的板塊模型，板塊間的交界帶有特別加深。圖片來源：Derrick Hasterok博士，阿德雷德大學
「我們探討了關於板塊邊界如何配置，以及過去大陸地殼如何構築的現有知識，」阿德雷德大學地球科學系的講師Derrick
Hasterok博士表示。他主持的團隊建立了這些新模型。
「陸地跟拼圖有點類似，隨時都是由好幾個片拼接而成，但這幅拼圖每次完成之後就會再次分割，重新排列而產生新的圖樣。我們的研究可以闡明這些形狀各異的拼圖有哪些，使得地質學家可以拼湊出過去的圖樣。」
「我們發現屬於板塊邊界的區域在地殼中佔了快要16%，而且在陸地的佔比更高，來到27%。」
團隊建立了三種新的地質模型：板塊模型、地體模型與造山運動模型。
Hasterok博士表示：「總共有26場造山運動——也就是形成山脈的作用——在現今的地殼架構中留下了痕跡。雖然並非全部，但它們很多都跟超大陸的形成有關。」
「我們的成果讓我們可以更新課堂教科書上看到的板塊分布圖以及陸地的形成過程。這些根據地形模型以及全球地震活動結合出來的板塊模型，在2003年之後就沒有更新過了。」
這座新的板塊模型納入了幾個新的微板塊，像是位在塔斯馬尼亞南邊的麥考利微板塊，以及分開印度板塊和澳洲板塊的魔羯座微板塊。
Hasterok博士表示：「為了讓這座模型更加豐富，我們對於屬於變形帶的板塊邊界類型加入了更加精確的資訊，先前的模型把它們描述成各自分離的區域而非一個寬廣的地帶。」
「這座板塊模型改變最大的地方在於北美西部。此處和太平洋板塊的交界通常會畫成聖安地列斯斷層和夏洛特皇后斷層。但是這道交界跟先前作圖裡狹窄的區域比起來，新劃分出來的要寬了大約1500公里。」
「另一個重大的改變在於中亞。新模型納入了印度像推土機一樣撞進歐亞板塊時，在印度北方產生的所有變形帶。」
團隊發表於期刊《地球科學評論》(Earth-Science Reviews)的成果，不但更加精確地呈現了地球的架構，也給出了其他重要的啟發。
Hasterok博士表示：「我們新建立的板塊模型可以更好地解釋90%的地震發生地點，以及80%最近二百萬年來形成的火山為何會這樣分布。相較而言，現有的模型只能囊括65%的地震。」
「板塊模型可以用來改進預測地質災害的模型；造山運動模型有助於了解地球動力學系統，並讓我們更準確地模擬地球的演化過程；地體模型則可以讓礦物的探勘過程更有效率。」
進行這項研究的人員來自阿德雷德大學、塔斯馬尼亞大學、內華達大學雷諾分校與澳大利亞地球科學組織。
Updating our understanding of Earth’s
architecture
New models that show how the continents
were assembled are providing fresh insights into the history of the Earth and
will help provide a better understanding of natural hazards like earthquakes
and volcanoes.
“We looked at the current knowledge of the
configuration of plate boundary zones and the past construction of the
continental crust,” said Dr Derrick Hasterok, Lecturer, Department of Earth
Sciences, University of Adelaide who led the team that produced the new models.
“The continents were assembled a few pieces at a
time, a bit like a jigsaw, but each time the puzzle was finished it was cut up
and reorganised to produce a new picture. Our study helps illuminate the
various components so geologists can piece together the previous images.
“We found that plate boundary zones account for
nearly 16 per cent of the Earth's crust and an even higher proportion, 27 per
cent, of continents.”
The team produced three new geological models: a
plate model, a province model and an orogeny model.
“There are 26 orogenies – the process of mountain
formation – that have left an imprint on the present-day architecture of the
crust. Many of these, but not all, are related to the formation of
supercontinents,” said Dr Hasterok.
“Our work allows us to update maps of tectonic plates
and the formation of continents that are found in classroom textbooks. These
plate models which have been assembled from topographic models and global
seismicity, have not been updated since 2003.”
The new plate model includes several new microplates
including the Macquarie microplate which sits south of Tasmania and the
Capricorn microplate that separates the Indian and Australian plates.
“To further enrich the model, we added more accurate
information about the boundaries of deformation zones: previous models showed
these as discrete areas rather than wide zones,” said Dr Hasterok.
“The biggest changes to the plate model have been in
western North America, which often has the boundary with the Pacific Plate
drawn as the San Andreas and Queen Charlotte Faults. But the newly delineated
boundary is much wider, approximately 1500 km, than the previously drawn narrow
zone.
“The other large change is in central Asia. The new
model now includes all the deformation zones north of India as the plate
bulldozes its way into Eurasia.”
Published in the journal Earth-Science Reviews, the team’s work provides a more accurate
representation of the Earth’s architecture and has other important applications.
“Our new model for tectonic plates better explains
the spatial distribution of 90 per cent of earthquakes and 80 per cent of
volcanoes from the past two million years whereas existing models only capture
65 per cent of earthquakes,” said Dr Hasterok.
“The plate model can be used to improve models of
risks from geohazards; the orogeny model helps understand the geodynamic
systems and better model Earth's evolution and the province model can be used
to improve prospecting for minerals.”
The work included researchers at the Universities of
Adelaide, Tasmania, Nevada-Reno, and Geoscience Australia
原始論文：D. Hasterok,
J. Halpin, A.S. Collins, M. Hand, C. Kreemer, M. Gard, S. Glorie. New
maps of global geological provinces and tectonic plates. Earth-Science
Reviews, 2022; 104069 DOI: 10.1016/j.earscirev.2022.104069
引用自：University of Adelaide. "Updating our
understanding of Earth's architecture."
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