About two years ago, my wife and I switched to a memory-foam mattress, and we couldn’t be happier. Everything claimed by the late-night advertisements is true. The mattress subtly conforms to the shape of your body, removing pressure points, so that you feel as though you were sleeping on air.
Now, here’s the fun part: as soon as you get off the mattress, it slowly rebounds to the original shape. In fact, when the mattress is first shipped to you, it’s compressed to about the size of a sleeping bag. Once you remove the packaging, however, and break the vacuum seal, the mattress automatically expands to full size in less than an hour.
In geology, we find the same phenomenon. The Earth itself has something of a characteristic shape (not a perfect sphere), determined by how the underlying crust varies in thickness, composition, and density. But this shape can temporarily deform, either by adding mass to the surface, in which case it is locally compressed, or by removing mass, which allows the surface to uplift. This concept is called isostasy, and it is illustrated well in the following cartoon:
Interestingly, rocks are more compressible than water. When great masses of water or ice accumulate on land, for example in the form of ice sheets or lakes, the land surface depresses. Once that ice melts (such as with the Scandinavian Ice Sheet since the last Ice Age) or the water dries up (as with the Great Salt Lake), the land surface immediately rebounds to compensate for the lost mass, just like your foam mattress returns to its original shape. Hence, geologists speak of post-glacial isostatic rebound: the readjustment of the land surface following the disappearance of the great ice sheets that once covered it.
A ‘Biblical’ Ice Age?
In so-called “Flood Geology”, young-Earth ministries such as Answers in Genesis and the Institute for Creation Research depend on the notion of only one ice age, albeit in several phases, which began shortly after Noah’s Flood and lasted centuries at most. They recognize the overwhelming evidence for widespread glaciation in recent Earth history, but cannot account for the time needed to grow and melt these massive ice sheets. Therefore, the timeline is arbitrarily compressed (disregarding the physical evidence and natural law) and allusions to icy weather are cherry-picked from the biblical text.
These young-Earth ministries have been astonishingly effective in persuading Christians of a “post-Flood Ice Age”, as though it were part and parcel of the gospel itself. But you ought to know that the concept is a pure fabrication of the modern creationist movement. First of all, the Bible is silent about ‘ice ages’ (because it was penned ~12,000 years after the last one ended), and to pretend that books like Job allude to icy conditions is intellectually dishonest. To know anything about past glaciation, we all rely on the historical sciences and geological data.
Interestingly, although YEC’s utilize historical science to acknowledge the existence of past ice ages, they abandon historical science when trying to answer the more important questions: How long did they last? How many were there? How much of the surface was covered with ice? What caused the extensive glaciation? And so their concocted story—the ‘Post-Flood’ Ice Age—becomes a walking contradiction, just like their methodology.
Post-glacial isostatic rebound defies the so-called biblical timeline
Could the extreme conditions following Noah’s flood have induced a comparably rapid ice age, which lasted only centuries? No, not at all. By the most basic laws of physics, we can say with confidence that it simply couldn’t happen. But let’s suppose, for the sake of discussion, that it did. What kind of evidence would that leave behind? How could we tell the difference between an ice age lasting centuries versus an ice age lasting tens of millennia?
Several days ago, I saw the following graphic shared in a group on Facebook. It plots the rates of isostatic rebound and depression across the surface of the Earth, as measured precisely by satellite. Where the graphic is red, the surface is rising, due to mass lost; where the graphic is blue, the surface is falling, due to mass gained [note: units are in mm/yr]:
You should notice first that isostatic rebound is occurring everywhere that we find evidence for continental ice sheets during the last glacial maximum, mainly across Antarctica, Canada, and northwestern Europe. And so the question was posed, along with this graphic: if Noah’s Flood really were global, shouldn’t we find isostatic rebound everywhere on Earth?
It’s a fair question. If the whole of Earth’s surface were covered in hundreds of meters of water, then we might infer that it should still be rebounding after the recession of the flood waters from the continents. However, one variable explains why the hypothesis doesn’t quite work: time.
If a global flood occurred, then according to the YEC, it lasted only ~1 year. This interval simply does not provide enough time for the Earth’s surface to compress in response to the excess mass. But that invites the question, how much time is required to compress the surface, so that it would still be rebounding today?
Unfortunately, that is a question for the geophysicist, since it involves a complex mathematical model, but the question has been answered. Depending on the nature of the underlying rock, it would take several thousand years at a minimum both to compress and to relax the rock.
In other words, if the most recent ice age lasted only a few centuries, as posited by folks like Andrew Snelling, then we should not observe significant isostatic rebound today where those continental ice sheets once existed. But we do, precisely as predicted by the conventional age of the ice sheets (~21,000 years old) and the timing of their final disappearance (~11–6,000 years ago). These observations flatly contradict the arbitrary YEC timeline for the last great ice age.
For the sake of discussion, however, let’s assume that we’re wrong about the time required to depress the Earth’s surface and induce isostatic rebound. Nonetheless, the YEC is left with a serious dilemma. We know from a plethora of geological evidences that multiple ice ages occurred during the last 1 million years. For example, we find glacial sediments in central and southern Siberia, which correspond to a much older glaciation (~500,000 years or more). During that time, the Eurasian ice sheet extended much further to the south. Similarly, we find glacial sediments in eastern Siberia, which date to the beginning of the last ice age, some ~90,000 years ago. Early on, the Scandinavian Ice Sheet extended far to the east into Asia.
While the YEC would dispute the absolute ages, they cannot deny what these sediments represent: continental ice sheets once covered much greater parts of both Asia and North America. In fact, YEC’s account for these data by claiming that the ‘post-Flood’ ice age simply occurred in multiple stages. But if that is the case, then all stages of the ‘biblical’ ice age occurred within centuries of each other, and all within the last 4,000 years. Geologically speaking, they are the same age.
Why, then, do we only see isostatic rebound today in regions where glacial sediments date to ~21,000 years old? Why is there no isostatic rebound in central and eastern Siberia? If you are a geologist, then the answer is rather straightforward: those ice sheets disappeared so long ago, that the Earth’s surface has already rebounded to its original shape.
The ‘Biblical’ Ice Age is a Creationist Myth
We cannot accept the claim to a ‘biblical’ ice age, which is a poorly fabricated myth of the modern creationist movement. This rationalization of the evidence highlights the anti-scientific nature of ministries like Answers in Genesis. Although they offer to us an answer for every question, those answers are known in advance of the investigation, and the evidence is warped around them. Thus upon careful analysis, the web of contradiction untangles, and along with it, the unsupported framework that is ‘Flood geology’.
Featured image: A Norwegian fjord, testament to large-scale glaciation in recent Earth history