A study published in the Proceedings of the National Academy of Sciences (PNAS) by Michigan State University researcher Dalton Hardisty and colleagues from the University of Hamburg and ETH Zurich reconstructed Earth's iron record over the last 1.2 billion years. ^[1] The researchers found that Earth's iron record also reflects continental weathering and the rise of land plants, not just ocean oxygen levels, broadening its use for interpreting Earth's history. ^[2] Dalton Hardisty and colleagues from Michigan State University, the University of Hamburg, and ETH Zurich found that Earth's iron cycle records changes in mountain building and the rise of land plants in addition to oxygenation. ^[3] Land plants accelerated iron delivery to the ocean by releasing chemicals that break down rocks and by holding streambed sediments in place, allowing more time for iron to react with oxygen and form iron-oxide minerals that can be carried to the ocean. ^[4] Peaks in Earth's iron record coincide with major mountain building events over the past 500 million years, including the Variscan orogeny that led to the formation of the supercontinent Pangea. ^[5] Land plants accelerated iron delivery to the ocean by releasing chemicals that break down rocks and by holding streambed sediments in place to allow more time for iron to react with oxygen. ^[6] The study analyzed sedimentary geochemistry data spanning the last 1.2 billion years to reconstruct the iron record. ^[7]