Earth's Icy Past Has Yielded Bountiful Food & Beauty
Next time you open the refrigerator and stare at the options, be grateful. Let that slight draft of cool air remind you of Earth's ice history and how that ice has formed global features that allow the planet to grow food to feed billions of people.
Ice ages have been rare in Earth's 4.56-billion-year history; ice age cycles have been even rarer. But only an ice age cycle permits the existence of a large human population capable of launching and sustaining civilization—part of which includes growing an abundant food supply.
In the past two billion years, ice ages have occurred in only three of the 21 geological periods prior to our own, and those ice ages were relatively brief. However, over the past 2.59 million years, a geologic age known as the Quaternary period, which includes our own time, thick sheets of ice have covered at least 10 percent, and as much as 23 percent, of the continents.
One extraordinary feature of the present glacial age is that it coincides with a period when the Sun is at its brightest and when atmospheric greenhouse gases are abundant. The present glacial era is also cyclical, meaning that the ice coverage of the continents oscillates rhythmically from 10 to 23 percent within a period of either 41,000 or 100,000 years, a feature that is essential for human flourishing.
Continents Move Perfectly into Place
Five amazing tectonic events have created the current delicate balance between ice and no ice:
1. The breakup of the supercontinent Pangaea resulted in a remarkable alignment of continents. Landmasses, not oceans, came to dominate the high latitudes of the Northern Hemisphere, and the Arctic Ocean became a nearly enclosed sea. Because continents have a much lower heat capacity compared to oceans, such a continental arrangement dramatically cooled the high northern latitudes and played an important role in the formation of the polar ice cap.
2. Antarctica split off from Australia and centered on the South Pole, surrounded by open ocean. Between 3.15 and 2.75 million years ago, about 8 million cubic kilometers (2 million cubic miles) of additional ice was deposited on Antarctica.1 Increased ice coverage and Antarctica's geographical location initiated stronger heat transfer from the North Atlantic Ocean to the deep parts of the Pacific Ocean.2 This heat transfer substantially cooled the Northern Hemisphere and, thus, contributed to its glaciation.
3. About 3 million years ago, converging tectonic plates led to the formation of a land bridge that connected North and South America. This isthmus cut off water flow between the Pacific and Atlantic Oceans, which forced a rerouting of ocean currents and atmospheric circulation. These new currents and circulations provided a more even distribution of precipitation on the continents, a crucial requirement for the launch and spread of future civilizations. (Obviously, humans need rainfall for crops wherever they choose to live.)
Forcing currents and wind patterns more into north-south, rather than east-west, directions also had a global cooling impact. In particular, the Gulf Stream brought atmospheric moisture into the Arctic region, which contributed to the formation of ice caps over the Arctic Ocean and Greenland.
4. The movement and uplift of Greenland also contributed to the establishment of the current ice age cycle. Recently, a team of geophysicists demonstrated that over the past 60 million years, Greenland has moved northward by 18° latitude. They showed that a "northward rotation of the entire mantle and crust toward the pole, dubbed True Polar Wander," moved Greenland 12° north.3 Plate tectonic reconstruction then moved Greenland another 6° north, relative to the mantle.
Meanwhile, during the past 5 million years, mantle-plume pulses lifted the eastern parts of Greenland to elevations exceeding 3,000 meters (10,000 feet) above sea level. The combination of Greenland's northerly location and high elevation above sea level decreased its temperatures enough to sustain long-term glaciation. Today, an ice sheet covers 81 percent of Greenland and has reflected more of the Sun's heat and light away, thereby cooling the entire planet.
5. Continuing collision of the Indian subcontinent with Eurasia caused the uplift of the Tibetan Plateau. About 2.59 million years ago, the ongoing collision between India and Asia pushed the Tibetan Plateau up to an average elevation of about 4,000 meters (13,125 feet) above sea level.4 This average height was sufficient for permanent ice to begin to form. When covered in snow and ice, the Tibetan Plateau, because of its low latitude (26-37° above the equator), has a powerful cooling effect on our planet. It reflects solar heat four times as efficiently as an equivalent area of ice-covered arctic landmass.
Tilted Toward a Minimal Ice Age
All in all, given how bright the Sun is now, it is truly remarkable that Earth is presently experiencing an ice age. Nothing less than the just-right combination and near-simultaneous occurrence of these five tectonic events would be adequate to produce an ice age at this time.
However, the present ice age is much less extensive than the ones that occurred prior to three million years ago. The minimal nature of the current ice age makes its cyclical property possible.
The collective effects of periodic changes in Earth's orbit and rotation on its climate, known as Milankovitch cycles, drive the cyclical property of the current ice age. One such variation occurs in Earth's obliquity, that is, the tilt of its rotation axis relative to the plane of its orbit. This varies between 22.1° and 24.5° within a period of 41,000 years. The greater the tilt, the greater the temperature difference between summers and winters worldwide. Given the current sizes and configurations of the continents, a lesser obliquity generates a global cooling effect, whereas a greater obliquity has a global warming effect.
Moreover, like all planets, Earth's orbit has an elliptical shape. Its orbital eccentricity, that is, the degree to which its orbital ellipse deviates from a circular shape, varies between 0.000055 and 0.0679. Earth's two most dominant eccentricity variation cycles historically last about 400,000 years and 100,000 years, respectively. Typically, such cycles would have only a subtle influence on a planet's global mean temperatures. However, when a planet is as delicately balanced as Earth is now—between an ice age and no ice age—the impact is more significant.
Benefits: Food, Civilization, Beauty
What have all these physical features produced?
From 120,000 to about 12,000 years ago, Earth's climate was so variable as to render the launch of human civilization impossible. As one research team demonstrated, the "last glacial climates were extremely hostile to agriculture."5 But when climate variability ended 12,000 years ago, the warm interglacial period also began, and these two factors not only made agriculture possible but also enabled agriculture and the civilizations based upon it to increase in sophistication all over the world. These factors, in turn, made possible the growth of the human population up into the billions.
Fields of ice from the last ice age continue to melt, feeding the rivers that water the great agricultural plains upon which seven billion people and their animals depend for their food.
From the high plateaus and slopes that were exposed at the close of the last ice age, mineral-rich dust and silt, known as loess, was blown by the wind onto many lowland plains, providing the crucial nutrients that make their soil fertile. The retreating of the ice fields and glaciers also concentrated many mineral ores in places and exposed many other valuable mineral deposits. Thus, the end of the last ice age contributed greatly to the launch of metallurgy.
As the vast sheets of ice covering much of the continental Northern Hemisphere retreated, they scoured out numerous basins, creating multitudes of large lakes. All these surface freshwater areas facilitate the processes of evaporation and condensation, which in turn produce precipitation over large swaths of land that otherwise would be barren deserts. In addition, lakes and rivers have provided humans with efficient transportation corridors and hydroelectric power resources.
The severity of the last ice age created enormous ice sheets spreading out over much of the landmass of the continents all the way to the seashores. As these ice sheets retreated, they gouged out fjords and inlets. These fjords and inlets created magnificent harbors all over the world.
We also have the last ice age to thank for people's ability to migrate from their original locales and eventually colonize and inhabit six of the seven current continents. The ice caused sea levels to fall to about 125 meters (410 feet) below current levels, which uncovered land bridges joining Siberia to Alaska, Britain to France, Asia Minor to the Greek Peninsula, Korea to Japan, Denmark to Sweden, and Vancouver Island and the Queen Charlottes to the British Columbia mainland. It also yielded easy island hops between Southeast Asia and Australia.
Of course, colonization also required that the continents be at a just-right distance from one another. This way, the ice age cycle could both close and open land bridges, and mountain elevations would tend to rise the closer one got to the equator. This meant that melting ice and snow could be more evenly distributed over the continental landmasses. Also, it was crucial that the sizes, shapes, and positions of the continents at the time of human habitation be exactly what and where they are today.
The last ice age also contributed an aesthetic benefit. Earth today is endowed with the most spectacular and beautiful scenery it has ever possessed. The receding ice sheets and glaciers have enhanced the relief of its mountains and valleys. They have created stunning waterfalls. They have nurtured an enormous number of meadows, forests, rivers, and lakes, all filled with an extravagant variety of plants and animals that display every imaginable combination of color and texture.
It appears that forethought has gone into the fashioning of all this stunning natural beauty, not the least of whose benefits is that it helps people maintain their sanity in today's high-tech, high-stress society. To put it another way, it seems that God optimally prepared and designed Earth and all its life throughout all of its history to provide for our aesthetic as well as our physical needs.
Hugh RossPhD, is an astrophysicist and the founder and president of the science-faith think tank Reasons to Believe (RTB).
Get Salvo in your inbox! This article originally appeared in Salvo, Issue #33, Summer 2015 Copyright © 2026 Salvo | www.salvomag.com https://salvomag.com/article/salvo33/glacial-blessings-flow
