2 weeks Ago By Amit Malewar
Earth's first crust composition discovery rewrites geological timeline. Earth and other rocky planets likely developed a primitive crust early on, but their chemical makeup hasn’t been studied much. This crust formed when materials from a vast magma ocean , created during planetary formation, were separated.
Experiments and timelines suggest that the molten rock rising from this magma ocean interacted with metals as they settled to form Earth’s core, or this happened after the metals had already been extracted. Scientists have long sought to determine when plate tectonics—the process that shaped Earth’s surface —first started, as it’s linked to the early development of life. Rocks formed in areas where tectonic plates collide and one slides beneath the other (subduction zones) have a unique chemical trait: they contain very little of the element niobium.
Researchers once believed that determining the age of the oldest low-niobium rocks could reveal when plate tectonics began. However, despite numerous attempts by various teams, their findings were surprisingly inconsistent. With collaborators across six universities, Professor Emeritus Simon Turner from the Faculty of Science and Engineering at Macquarie University has made a breakthrough discovery that changes our understanding of Earth’s early geological history .
It reveals that Earth’s first crust, formed about 4.5 billion years ago, probably had chemical features remarkably similar to today’s continental crust. It’s long been thought that tectonic plates needed to dive beneath each other to create the chemical fingerprint we see in continents.
The research shows this fingerprint existed in Earth’s first crust , the proto-crust, meaning those theories must be reconsidered. The team simulated conditions on early Earth using mathematical models of when the planet’s core formed, and a molten rock ocean covered its surface. Their calculations revealed that Earth’s first crust, the proto crust from the Hadean eon (4.
5–4 billion years ago), could have developed chemical traits similar to those of modern continents without relying on plate tectonics. The model’s early findings revealed that the element niobium would be drawn to metal in the oxygen-poor environment of early Earth—a trait known as siderophilic behavior. As a result, niobium would sink through the planet’s molten magma ocean and become part of the Earth’s core.
The link was identified between early core formation , patterns of siderophile elements, and the negative niobium anomaly in the continental crust. The crust’s unique chemical signature aligns with material removed from the mantle after the core formed before meteorites impacted early Earth. This explains why the signature is consistently found in continental rocks across all ages.
The research reveals that the chemical signatures in continental crust were established during Earth’s earliest phase, unaffected by surface activity at the time. This initial crust was transformed and enriched with silica through meteor impacts, fragments breaking off, and the onset of plate movement. The early crust likely fragmented, thickening certain regions and laying the groundwork for the first continents.
As these fragments shifted, molten magma filled the gaps, forming a crust similar to today’s ocean floors. The intense meteor bombardment during Earth’s early history caused significant disruption and reshaping of the crust. Plate tectonics likely operated irregularly, driven by these meteor impacts, until around 3.
8 billion years ago, when the bombardment subsided as the solar system became more stable. After this, plate tectonics settled into a continuous, self-sustaining process. Journal Reference: Turner, S.
, Wood, B., Johnson, T. et al.
Formation and composition of Earth’s Hadean protocrust. Nature (2025). DOI: 10.
1038/s41586-025- 08719-3 Topics Earth's core Ocean Plate Tectonics.
