An excellent question. Let me elaborate.
One of the most basic ideas in Geology is that the present is the key to the past. If you see the process or phenomenon happening today, then you can assume it also occurred in the past and so better understand what the rocks are trying to tell you. For example, we know that glaciers in the modern world leave big scratch marks in the rocks where the ice has scraped past, so if we see those same scratches in ancient rock formations, we can infer that there was once a glacier there, even if those rocks are now sitting in a desert. Simples.
Another important idea that has been gaining momentum in recent decades is that the past is the key to the future. So if you know something happened in a certain way, with certain effects, in the past then there’s a good chance it might happen again in a similar way in the future. History has a habit of repeating itself, after all.
One of the most important issues we can apply this idea to is modern day climate change.
We know we are adding carbon dioxide (and methane, water vapour, nitrous oxide etc.,) into the atmosphere through the burning of fossil fuels. We know that these gases are greenhouse gasses and will cause Earth to warm. We know if we warm the Earth enough, then one of the effects will be to melt the polar ice caps (and high altitude mountain ice), raising sea level and jeopardizing the lives of millions of people. That’s on top of other more insidious effects such as ocean acidification and decreasing food crop yields.
This is all basic physics, so there’s nothing really to debate here (despite what certain “skeptics” would have you believe). But… there are lots of unknowns about the precise effects of climate change on the sensitive climate and ecological systems, including the future behavior of the monsoons. We suspect the monsoons will change as the planet warms – the monsoon rains are ultimately driven by seasonal changes in heating over Asia – but we don’t know in which direction. Will it get rainier or drier? Will the season of maximum rainfall shift? Will the same amount of rain fall in greater or fewer months of the year?
From an agricultural and policy planning point of view, these details are absolutely vital.
So that brings me back to ocean mud; what can it possibly tell us about future monsoons??
You can think of the oceans as gigantic bowls or basins, into which all the rock and mud that has been eroded from the land will eventually collect, washed in by rivers the world over. So you can imagine that over time the mud collects in layers at the bottom of these giant bowls recording the history of all the rock that has been eroded from the land over the millennia. At the bottom is the very oldest mud, with the youngest mud deposited on top at the sea floor. Mixed in with this rock are things that live in the (fish) bowl, from tiny microscopic plankton to the great whales. These too will eventually settle into the depths of the ocean bowl upon death, to be incorporated in the great muddy ticker-tape of time.
(Literally nothing about this image is to scale)
So when we come along with our big drilling ship, and stick a glorified steel straw into this mud, what we pull out will record the history of erosion and deposition from that region far back into the past (indeed, as far back as we are able to drill down).
And that is what we are doing on IODP Exp. 353.
We are collecting hundreds of meters of this mud, the deepest parts of which can take us back in time to when the dinosaurs were still stalking the Earth, some 75 million years ago. We can use it to look at the behavior of the monsoons, and other phenomena, during periods of time when CO2 was equal to or higher than it is today (about 400 parts per million). Once we understand how the monsoons behaved in this ancient warmer world, we will have a better idea of how it might behave in the coming centuries.
Once we are back on shore (and in our nice comfy labs again), we will take this mud and analyse it using various nifty sedimentological (mud-bothering), geochemical (chemical-bothering) and paleontological (biological-bothering) techniques, until the mud gives up it’s oozey secrets and tells us everything we want to know about the ancient Indian monsoon. But that’s a story for another day…
In the meantime, this is how a bunch of scientists try and decide where the K-T boundary is… pointing and guesswork!
(p.s. Wolfgang was right!)