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Impact craters often have asymmetric shapes, which have been used to infer the direction and angle of impact. But pre-existing structural or topographic heterogeneities also play an important role in crater asymmetry.
Rising carbon levels contributed to profound climate change 55 million years ago. Where did that extra carbon come from? One proposal — a cometary impact — is rebuffed by two analyses of magnetic particles in clay sediment cores from New Jersey.
India and Arabia collide with Eurasia at slightly different velocities. Detailed mapping of the Arabian Sea suggests that this motion started between 3 and 8 million years ago, possibly with a transfer of an Arabian plate wedge to the Indian plate.
In aerosol hot spots around the globe, solar radiation is dimmed down on its way to the Earth's surface. The resulting surface cooling turns out to be almost in balance with heating of the atmosphere due to black carbon.
Neither recycled oceanic crust nor sediments alone can explain the composition of ocean-island basalts, but how about a mixture of the two? Recent modelling using the isotopes of hafnium and neodymium appears to support this contention.
Modern deep waters form in the Nordic seas when high-salinity surface waters cool and sink. An analysis of Arctic Ocean sediments suggests that throughout the past fifteen million years, brines created during sea-ice formation controlled the sinking of water.
The atmosphere's lowermost 10 km have long been assumed to be almost solely responsible for weather and climate on Earth. Emerging evidence points to the layer above as an important influence on surface winds and temperatures on seasonal to decadal timescales.
From about 470 million years ago, the Middle Ordovician period witnessed a rapid increase in biodiversity. This explosion in numbers of species is almost perfectly contemporaneous with an increased frequency of meteorite impacts.
The relationship between carbon dioxide and climate over millions of years has been a source of controversy. Fossilized liverwort leaves can help illuminate both temperature and atmospheric carbon dioxide levels from 200 to 60 million years ago.
