I’m sure if I asked you to step a mere 1,000 years into the past, you’d likely encounter a vastly different climate. If I we were to go a little further, say 20,000 years, there may very likely have been a few kilometres of ice over your head. Climate does change.
Climate Changing in Recent Years
In recent years, we’ve heard increasingly about the concerns regarding climate change. It’s primarily tied to the role we’ve played in the changing of that climate. The degree to which this is an issue isn’t of too much concern right now. Rather, it’s important to realise, change is an inherent element of climate. In fact, it’s been doing so for millions of years. And it’s not about to stop any time soon.
Our one hurdle is simply because we live amidst certain conditions to which we’ve grown accustomed. If you’re in the northern part of North America, you’d say something like, ‘it always starts to snow around a certain time.’ Or, ‘there’s never any snow at Hallowe’en.’ Maybe, ‘the leaves usually begin to fall at such and such a time.’ So, we’ve snuggled into the world being a certain way. It matches our expectations. Unfortunately, it’s only that way for a relatively short time.
Ice Ages Over the Millennia
Globally, scientists have been able to identify five significant ice ages over a very long period of history. Scientists go by ice ages because, over time, our planet cycles through periods when global temperatures are cold enough to permit continental ice sheets and alpine glaciers to persist on the surface.
There have been five major ice ages with the earliest 2 billion years ago. They include the Huronian (2.4-2.1 billion years ago), Cryogenian (850-635 million years ago (mya)), Andean-Saharan (460-430 mya), Karoo (360-260 mya) and Quaternary (2.6 mya-present). The Quaternary is divided into two epochs: the Pleistocene (2.6 mya to 11,000 years Before Present or BP) and the Holocene. That’s the one we’re currently in.
Within an ice age, there are interglacials. Interglacials are just warmer periods within an ice age where there’s maybe only one major ice sheet.This is the interglacial period we’re currently experiencing that began around 11,000 years ago BP.1
Why Ice Ages Develop
Ice ages are often tied to the movement of the continents. That’s ongoing, too. When continental movements shift the plates2 in such a way to obstruct customary ocean or atmospheric circulation patterns, this can trigger an ice age. At the height of the most recent ice age, the ice grew to be more than 3857.6 m (12,000 ft) thick.
Other factors include cyclic changes in Earth’s orbit. This alters the amount of sunlight reaching the surface. This, too, can jumpstart an ice age. It’s worthwhile to remember that both Greenland and Antarctica are not a permanent feature of our planet. They just are now.
Ice core sample taken from drill.
How scientists can tell when an ice age occurred involves knowing where to look. They’ve discovered that examining and analysing ice cores taken from glaciers yields valuable information. For instance, the little air bubbles are like little time capsules for atmospheric conditions, sometimes millennia in the past. They provide a little insight for a few hundreds of thousands of years.3 Meanwhile ocean sediment cores allow scientists to peer millions of years into the past. Simple layers of dust, pollen and other remaining debris can tell scientists a lot about the past.
EFFECT OF THE ICE AGE ON THE CAPE SHORE AND BURIN PENINSULA
The ice age peaked about 20,000 years ago and our warm interglacial began about 11,000 years ago. Here, around Placentia Bay, the evidence of the ice age is abundantly clear.
Researchers have told the story of the glaciers by reading the striations left by the glacier. Striations are deep scratches on rocks left by the ice as it ground by overhead. They’d be largely unnoticeable unless you’re aware of what had happened.
On the Burin, striations spoke of how much of the glacial flow was initially flowing south-southeastward. Much of the large-scale landforms resulting from glaciation run parallel to what the striations confer. It moved across the peninsula and further onto offshore islands such as Merasheen.
A second phase of glacial flow trended southwestward in the north and northwestward in the south and the third phase had ice flowing north-northwestward possibly from offshore.
Striations again feature on the southwest Avalon. Located in Cuslett Cove and Angel’s Cove, striations mark the movement of ice on the Avalon. The shifting of the ice can be understood as occurring in threee phases.
In Phase 1, during the last glaciation, the ice was centred on the southwest Avalon in what was termed the Castle Ridge ice centre. Glacial ice flowed south, parallel and then along the shore of Placentia Bay.
At about this time, the ice further thickened and slowly flowed along what we now know as the Northeast and Southeast Arms in Placentia. Anyone sailing their boat along these waterways nowadays would be shocked to know their origins. But it’s the phenomenal weight of the glaciers that dug through the sediment and rock to create deep glacial valleys.
Beginning with the creation of the St. Mary’s Bay ice centre, during Phase 2, this ice gradually grew in size, eventually covering the southern two-thirds of the Avalon Peninsula.
During the Late Wisconsin glaciation, Placentia Bay was completely covered with ice. The Wisconsin glaciation was one of several that comprised the North American ice sheet complex.
Striations on rock behind Visitor Centre of Castle Hill Historical Site of Canada.
The ice moved in a southwest direction and this is yet again visible in striations gouged into the rocks that had lain there for millennia. If we stop in at the Visitor Centre of Castle Hill Historical Site of Canada, to its rear, it’s possible to find one example of striations left by the glacier.
By Phase 3, deglaciation was well on its way. Rivers were forming within the glacers in the valleys in which the Northeast and Southeast Arms later formed. This would leave eskers or long and winding ridges of sand and gravel.
These were deposited as the stream of melted water flowed within the glacier towards Placentia Bay. The transported sediment would create a large fan delta at the entrance to Placentia Bay.
Over the subsequent 5,000 years, the sea level has gradually risen, flooding the Northeast and Southeast Arms. A gravel pit now extracts the sediment deposited in the delta. There are numerous other indications of the previous ice age, such as erratics spotted across the countryside. These are rocks not native to the location where they’re currently situated, having been transported there by glacial ice.
A Climate Changing
All these changes point to a world that has radically transformed over the past millions of years. Are the changes in our climate due in part to a human impact or are we overstepping our role by saying so? It may be we’re having some impact, but there are a few things we need to bear in mind.
What we know without any question is over the past millions of years, our planet has undergone regular cyclical changes. These are supremely vast. For sea level alone, it’s estimated to have been 120 m lower during the most recent glaciation.
A normal progression will eventually see the end of the ice age in which we have lived our lives. The Antarctic and the Greenland ice sheet will be gone, the sea level will have risen, no doubt metres higher than it is currently.
Composite satellite image of Antarctica (2002).
The parts of our world where snow and ice rule the day will have transformed. In fact, it may return to how it was tens of millions of years ago. After all, in places such as Antarctica, we find petrified wood. They are the remains of trees that formed 40 million years ago, just as Antarctica was cooling down.
As certain as the revolution of our planet around the sun are the ongoing shifts and changes to our climate. They were occurring long before we appeared. We’ve only been in existence during the latter portion of the most recent ice age.
And those changes to the climate will likely continue long after we are gone, perhaps evolved into a different species entirely. A lot can happen in a few million years, which is a long time for us, but not so for the Earth.
We live on a magnificent planet in which we are only minor players, regardless of what some of us may think. Climate change is only one of the many systems that play a role in the intricate and masterly operation of our planet. Our climate changes as a matter of course and as we’ve done since we arrived on the planet, we will continue to adjust to whatever differences it brings. We will evolve.
2The earth’s crust consists of continental plates that move over the surface. Their interaction is what yields mountains and other surface features.
3The oldest continuous ice core records extend to 130,000 years in Greenland, and 800,000 years in Antarctica.