[comparison photos of glacier retreat in 20th century]
At least one of those photos is from Glacier National Park.
https://petapixel.com/2015/10/25/these-before-and-after-photos-show-how-glaciers-in-the-us-are-melting/
What that article and video fails to mention is that that area has been both under much more extensive glaciation AND TOTALLY FREE OF ANY GLACIATION MANY TIMES IN THE PAST (virtually every "interglacial" period prior to the current one being either 1. before human activity could have had any activity on climate, or 2. before any humans even existed). Not sure (haha!) why the people claiming that THIS current de-glaciation is caused by human activity and FAIL TO MENTION all the other numerous de-glaciations that occurred
without any possible influence of humans.
Here is an excellent brief paper (with maps) from the U.S. Department of Interior, U.S. Geological Survey regarding the intermittent glaciation of the Glacier National Park area:
https://pubs.usgs.gov/of/1993/0510/report.pdfSome excerpts:
INTRODUCTION
Glacier National Park presently contains only about 50 small glaciers. Many of
these glaciers are in remote and inaccessible areas rarely visited by anyone.
However, the park is applicably named as the spectacular scenery that surrounds the
visitor everywhere is due to
the great glaciers that occupied the park and surrounding
region until quite recently (geologically speaking, of course). These great glaciers
scoured the high areas of the park forming the jagged peaks and sheer walls that we
find so breath-taking. In the lower areas of the park these glaciers deposited their
great loads of debris damming many of the valleys and forming the beautiful large
lakes that the park is noted for. This pamphlet will provide you with information about
the glacial history of Glacier National Park, features of glacial erosion and deposition
in the park that you can see first hand, and some general information on glaciers and
ice ages.
THE GLACIAL HISTORY OF THE GLACIER NATIONAL PARK REGION
FROM THE TIME OF THE LAST MAJOR GLACIATION TO THE PRESENT
During the maximum extent of
the last major glaciation (the Wisconsin glaciation)
about 20,000 years ago, much of northwestern Montana, including the Glacier
National Park region, was covered by glaciers (fig. 1). To the west, the Cordilleran ice
sheet advanced into this region from Canada. The easternmost lobe of that ice sheet,
the Flathead lobe, flowed south into the present-day Flathead Lake area. To the east,
the Shelby lobe of the Laurentide ice sheet advanced from Canada across the
Montana plains almost as far south as the present-day city of Great Falls. Between
these two large ice sheets, valley glaciers and ice fields flourished in the mountains
along the Continental Divide. West of the divide, some of these glaciers merged with
the Flathead lobe of the Cordilleran ice sheet. East of the divide, glaciers advanced
beyond the mountain front onto the plains where they spread out laterally to form large
piedmont glaciers.
Deglaciation of the Glacier National Park region is thought to have been completed
more than 10,000 years ago. A volcanic ash that erupted about 11,200 years ago from
Glacier Peak volcano, about 350 miles to the west in Washington State, has been
identified at nine sites in the Glacier National Park region (fig. 2), where it rests on
glacial deposits. Therefore, this ash indicates that the underlying glacial deposits are
at least 11,200 years old. The locations at which this ash was found indicate that
deglaciation of the Glacier National Park region was at least 90 percent complete by
that time. Remaining glaciers, if any, were confined to valleys within the Livingston
and Lewis Ranges. By 10,000 years ago, remaining glaciers probably were confined
to those cirques and well-shaded niches where present-day glaciers and snowfields
lie.During the next several thousand years, temperatures in the Glacier National Park
region were several degrees warmer than they are now and there were fewer
glaciers. Some of the larger glaciers may have survived this warm period, but many of
the park's smaller glaciers probably did not exist at this time. This warm period ended
sometime between 5,000 and 3,000 years ago. [Note that they can't pin this down to a more
accurate time than 2,000 years earlier or later (and that was only 3,000 to 5,000 years ago)...
and people are now clamoring about things in mere human (perspective) lifespans... totally
lacking in geological perspective.] After it ended existing glaciers probably increased in size,
others may have been formed.
A significant advance of glaciers around the world, referred to as
the "Little Ice
Age", occurred between about AD 1500 and 1900. In Glacier National Park, glaciers
reached their maximum extent during the mid-19th century. Although glaciers
produced during this advance were small compared to those of full-glacial conditions,
this advance was the most extensive since the end of the Wisconsin glaciation. During
the Little Ice Age, there were about 150 glaciers in the park. These glaciers ranged in
size from small ice bodies of only a few acres to the Blackfoot Glacier, which covered
about 1875 acres and encompassed the area of the present-day Blackfoot and
Jackson Glaciers. The Mt Jackson area of the park contained 27 glaciers that totaled
about 5330 acres at that time.
Since the mid-19th century, glaciers in Glacier National Park have shrunk
drastically. Retreat rates were slow from the mid-19th century until about 1920.
However, from 1920 to the mid-1940's, above-average summer temperatures and
below-average annual precipitation in the Glacier National Park region caused the
glaciers to retreat rapidily; many disappearred altogether. After the mid-1940's, the
overall retreat rates slowed. A study by the U.S. Geological Survey in 1979
determined that 17 of the 27 glaciers formerly present in the Mt. Jackson area during
the mid-19th century no longer existed. The remaining glaciers covered only about
1830 acres.
Today, only about 50 small glaciers remain in Glacier National Park. These
glaciers range in size from just a few acres to the Blackfoot Glacier (fig. 3), the largest
in the park with an area of about 430 acres in 1979. Other sizeable glaciers in the park
include the Harrison (370 acres), Rainbow (260 acres), Sperry (250 acres), Jackson
(250 acres), and Grinnell (225 acres).
ICE AGES
Ice ages have occurred throughout the history of the earth. Geological evidence
suggests that
the first ice age may have occurred more than 2 billion years ago. These
past ice ages may have lasted 20 to 50 million years.
The most recent ice age (which
really hasn't ended) began several million years ago, and
as many as 17 major
glaciations have occurred during the last 2 million years. These major glaciations
were separated by periods of warmer climatic conditions and reduced ice cover.
During the maximum extent of the last major glaciation, about 20,000 years ago, large
ice sheets covered much of North America, Europe, and Siberia. In addition, the
Greenland and Antarctic ice sheets were thicker and more extensive than today.
Altogether, glaciers covered about 30 percent of the world's land surface at that time
compared to the 10 percent they cover today.
Many processes have been proposed to explain the cause of ice ages. These
processes include continental drift, mountain building, volcanic activity, changes in the
sun's output, and changes in oceanic or atmospheric circulation. Currently, many
scientists favor the Milankovitch theory, named for a Yugoslavian mathematician. This
theory proposes that climate change is caused by changes in the geometrical
relationship between the Earth and the Sun, including variations in the tilt of the
Earth's axis and ellipticity of the Earth's orbit.
At the present time, we live in a period of moderate climatic conditions, when large
ice sheets cover only Antarctica and Greenland. Evidence suggests that these periods
of moderate climatic conditions represent only about 10 percent of the last 2 million
years. During this time, interglacial stages have lasted only about 10,000 years each.
Our present interglacial stage started more than 10,000 years ago and, hence, could
end soon.