THE ICE AGE STOPPED HERE
----------------------
John Pazmino
NYSkies Astronomy Inc
www.nyskies.org
nyskies@nyskies.org
2004 January 19
[This article was written before setting up the NYSkies website.
Except for trivial editing, mainly for typos, it is the original text]
Introduction
-----------
The Science Industry Business Library had a geology lecture on
2004 January 6 17:30 EST. The talk, 'The ice age stopped here' was
presented by Mr Fred Hadley, a local historian and photographer.
It was a very thoro and comprehensive discourse on how the last
ice age glaciers influenced the history of New York City. I offer only
a few highlights. What made Mr Hadley's lecture so fascinating was the
audio-video material: maps, photos, videos.
Mr Hadley was first struck by the idea that the ice age shaped the
City by looking out of his apartment window. His house, North Shore
Towers near the Queens-Nassau border, is near the highest natural
point in Queens with a dropdead panorama of the world. He noticed that
the prospect in each direction is radicly different. After some
reading and inquiries he undertaked a self-study of the ice ages.
Glaciers
------
He began by showing the topography of the City with its fabled
'terminal moraine' stretching clear across Staten Island, Brooklyn,
and Queens. While he stressed the City in his talk, he did excurse
onto Long Island from time to time.
Most New Yorkers are aware that the ice age had something to do
with the City. One of my friends asserts that the glaciers came to
rest in Green-Wood cemetery. I quipped that only some of the Glacier
family is there; the rest is in Evergreen, Cypress Hills, and certain
other cemeteries. This went right over her head
He gave a quickie lesson on glaciers by showing pictures from a
vacation trip to Alaska, which is laden with them. They recalled to me
my own experiences with the glaciers of Fjordland National Park in New
Zealand, including the skiplane flight to the top of the icepack.
A glacier is essentially a flow, slow, yes, of ice built up by
precipitation of snow. The most usual type is one that resembles a
river winding down a mountain. Snow falls in the colder regions on
mountain tops and then oozes down the slopes. On this theme, glaciers
are found not only in the polar parts of the Earth but on very high
mountains, like the Andes straddling the equator.
In the current era the Earth is in a warming phase, so many
glaciers are in retreat, as monitored by the operators of the preserves
and parks they lie within. Hadley showed pictures of some glaciers now
and several decades ago to demonstrate this feature.
The ice that inundated new York was so thick that minor relief it
passed over did not modify its progress. The ice flowed over more or
less level terrain near the City, somewhat like the ice on seas
surrounding Antarctica. Estimates of the depth of ice near the City
vary, but it's around a full kilometer ro two.
Geography quiz
------------
Fred tossed out a few geography questions while showing his slides
of Alaska. Which is the northernmost of the United States? That was
easy: Alaska. Which is the western most? Most of the audience answered
correctly: Alaska. They probably knew that the Aleutian island chain
extends awfully far west.
How about the southernmost? Many said Florida but several were up
to answering correctly for Hawaii. It's at about the same latitude as
Mexico City.
The easternmost? Here the audience fell apart. Just about all
offered Maine. Mr Hadley explained that it's Alaska! The Aleutian
islands reach over the 180th meridian to have EAST, not west,
longitude. I had to smile at this, it being nothing but a trick of
coordinates.
Later, when discussing Long Island, Hadley asked which is the
largest Island in the United States? Well, first off, the US doesn't
got many 'islands' as such, yet there are candidates along the east
coast. After dismissing Vancouver for being in Canada and a rather
good guess for Kitty Hawk (the Wright Brothers centennial is still
fresh in mind), it's Long Island.
New Yorkers kind of knew from childhood that Long Island is
special, It even has its own state abbreve, LI. It's included in all
but the very smallest scale of US maps, where all the other islands
shrink out of existence.
As long as we were on geography, Fred asked for the three
countries closest to the US. Indian nations don't count as actual
countries.
Mexico and Canada were obvious for being contingent on the US
frontiers. A few put up Quebec for #3, but technicly it is still part
of Canada.
Cuba? It is only 140Km from Key West. I remember seeing the light
dome of havana from the Winter Star Party in the early 1990s.
One person offered a tiny island near Maine that belongs to France
as an internal province rather than a colony. It turns out that this
island is really far from the US in the Gulf of St Lawrence.
The right answer is Russia! From the Cold War I knew about Big and
Little Diamond Islands. One is in Alaska; the other, Siberia. They
stand only 80 kilometers apart in the Bering Strait.
Terminal moraine
--------------
The last ice age, about ten thousand years ago, was the expansion,
due to a cooling of Earth's climate, out of the north polar regions to
the mid northern latitudes. A similar outswell occurred from the south
pole but there is less land around there to leave its marks.
It so happened that the farthest south extent was plumb smack
within the present praecicnts of New York City, on a line that arcs
across the United States to the Pacific coast. The particular glacier
that settled over the City is the Wisconsin glacier, one of four that
constituted the ice ages.
In time the ice melted and dropped its accumulated debris along
its front edge. This mishmash of assorted dirt, rocks, till piled up
as a ridge or berm or spine or dorsum. Along it today are the many
hoods with 'Heights', 'Ridge', 'Hills', 'Slope', 'Terrace' in their
names. The names reflect the hilly topography atop or aside of the
debris heap. This heap is the terminal, or end, moraine of that
glacier and is some ten thousand years old.
In absolute terms the moraine has only modest elevation, up to
about 75 meters above sea level. In general, it tapers lower from west
to east, with Todt Hill on Staten Island being not only the highest
spot on it, but highest natural point on the entire East Coast south
of Maine. Some other high places along it are, Ward Hill, Grymes
Hill, Green-Wood cemetery, Prospect Park, Celestial Hills cemetery
(No! I didn't make that one up!!), Houdini's tomb (I didn't make that
one up, either!!!). Against the surrounding lower land, the moraine
offers smashing vistas of the City.
The dirt got here from northern regions of the Earth by being
pushed by the front edge of the icepack, being entrained within its
bulk, and being dragged along by abrasion and scrapping. You can pick
up rocks quite foreign to the City, coming from New England, Quebec,
and Canada. This is specially so on the north side of the moraine
where the debris was piled up more densely.
Track of the moraine
------------------
The moraine runs southwest to northeast, then more east, thru the
City. On Staten Island it's the Greenbelt. The Narrows is a weaker
part of the moraine, along the line of the Verrazano Bridge (no, I'm
not sure which letters are geminated!). In Brooklyn it runs from Bay
Ridge, thru Prospect Park, to East New York, to Highland Park.
In Queens, it crosses from Forest Park to Glen Oaks. The Interboro
(Robinson) Parkway, Kew Gardens interchange, and Grand Central Parkway
sit on its crest or flank.
On Long Island the moraine continues to Roslyn Heights, where it
branches into a north and south prong. These run to the ends of Long
Island, forming the north and south forks, or flukes.
The history now is that only one glacier caused the two moraines
on the Island, not two separate ones as once believed. The glaciers
pushed to the southern moraine, mel/ted back to the northern one,
stood there for a while (decades?), then continued its migration
northward out of the City region. The land between these moraines is
flat, but elevated above that on the south side of long Island. It's
filled with detritus from the glacier that could not flow our to the
sea for the being blocked by the southern moraine.
The are gaps or passes in the moraine. The ones emphasized by Fred
are the Narrows, joining the upper and lower bay and in Jamaica. The
Narrows was at first merely a weaker section of the moraine. As the
sea rose, filled by the melting ice, it broke thru to be a major cut.
This is more or less the line of the Verrazano Bridge.
The moraine in general is today less severe in relief than in
colonial or even late 19th century times due to land working associated
with building up the City.
Ice cover
-------
All the City north of the moraine was under the icepack a
kilometer or more deep, including Manhattan. South of the moraine
there never was mass ice at all. The gentle slope of the southern face
of the moraine comes from the runoff of the melting ice with its
debris. This part of the City is the alluvial or outwash plain. Place
names here reflect the relief, such as 'Flatlands' and 'Flatbush' in
Brooklyn. This area contains the City's beaches, marshes, basins,
canals, lagoons, and sand bars.
The larger pieces were dropped near the face of the glacier, the
smalls were carried farther south. This is in fact what you find in
the soil of the City today. The rocky dirt is near the moraine while
the sands are along the south waterfronts.
You can see some of the rocks carried by the glacier and dropped
as the ice melted away in, for instance, Central Park. These are the
lonely boulders, some with deep scratches from being dragged and
scrapped. When the Park was built there was no good geology to explain
these rocks; after all, the orthodoxy of the time preached for a 6,000
year-old world.
Retreating ice
------------
After some while, perhaps a couple hundred years, the Earth warmed
up to begin the retreat of the icepack. During the ice age, water
normally in the oceans was sequestered in the ice, so the ocean level
was lowered. Fred noted that in the New York region the sea was some
90 meters lower and the shoreline was some 130 kilometers farther out
than now. Thus, there was none of the present hydrology around the
City at all; the ice sat entirely on ground.
Anthropologists and archaeologists believe there was human
occupance of the land from the frontage of the ice to the sea. This
supposition is based on evidence of the ice age in human relics found
elsewhere in the world. Now all of this turf is underwater, making it
just about impossible to explore these early habitations.
The ice did not actually reverse course and go back to the poles.
It melted in place, dropping its burden of material. Hadley explained
that Long Island Sound was at first a large lake, barraged at both
ends by the eastern part of the moraine and Hell Gate. As the waters
rose from filling by melting ice, these barriers were overtopped. The
lake then communicated with the ocean to become the Sound.
Today Hell Gate is still a shallow part of the Sound, a submerged
weir so to speak, perilous to unwary boats and ships. This is why all
ocean shipping approaches the City from the south, the bay, to make
the southern part of Manhattan the first section to build up.
As the ice melted off, large chunks broke off and lingered on the
ground, These softened and washed out the soil under them to form
round deep lakes, kettle lakes from their cross section shape. Lake
Ronkonkoma and Lake Success on Long Island are two notable examples of
these glacier-created features.
Use of the land
-------------
The use made of the land was heavily influenced by the moraine.
Hadley showed pictures and maps of cemeteries (remember the friend I
mentioned?), parks, golf courses, country clubs, water works. These
were all purposefully put on the moraine (without realizing what the
topography was) to avail of its elevation and topography.
In the flat plain to the south were racetracks and airports and
beaches, which can do very well without interfering relief.
It was amazing to see from thematic maps of the City just how
tightly these features delineate the moraine!
You can repeat Hadley's demonstration with photocopies of a metro
New York road map. On one copy highlight all racetracks. On an other
highlight the country clubs. And so on. Be sure to include retired
facilities, like Roosevelt, Miller. Floyd Bennett Fields (airports)
and Gravesend, Sheepshead Bay, Jamaica (racetracks).
Holding these maps at armslength dramaticly shows the bias of
these features with the moraine!
Revolutionary War
---------------
He expounded on the role of the moraine in the American
revolution. The Americans, with only a few thousand irregular troops,
held positions atop the moraine, the better to keep watch of the
British armies to the south on the alluvial plain. The moraine was
then called 'wooded hills of Gowanus' with no inkling of its
geological nature.
England moved one army thru the gap in Jamaica to trap the
Americans between armies of quite greater number and strength than
they had. This outflanking forced the Americans to flee across the
East River to Manhattan.
Heavy casualties were suffered by Americans during their flight
from the British in this, the Battle of Brooklyn (or of Long island).
Thruout the entire Revolutionary War, about 1/2 of all American losses
were taken in skirmishes associated with the terminal moraine.
Long Island Railroad
------------------
He showed the life of the Long Island Railroad. There was the
desire to build a railline from New York to Boston in the 1830s but
the shoreline along Connecticut was too rugged for the construction
techniques of the era. The flat lands of Long Island, south of or
between the moraines was perfect for laying the rails from Long Island
City to Greenport.
From there you took a ferry to eastern Connecticut on more flat
turf well north of the moraine. From there you continued to Boston on
the Old Colony line. The journey took one full workday rather than
three full days by horse-hauled coach.
Just about when the line was finished, engineering progressed
enough to build the New haven line, which offered a one-seat ride
taking about six hours. This just about killed the LIRR, which
eventually reconstituted itself into the present regional rail
service.
If you're up to the challenge, you can today retrace the original
route. The LIRR still runs from Long Island City to Greenport; the
ferry still runs from Greenport to (I think) New London, Connecticut.
From there Amtrak brings you to boston. (Yes, this itinery will set
you back about the same 10 hours!)
The videos
--------
The heart of Fred's lecture were the several videos. These were a
mix of simple camcorder shots of a reenactment of the Battle of
Brooklyn in 2001, driving along certain highways that align with the
moraine, tours of Floyd Bennett Field as an airport example.
The grandest video was a flyover of the City in a hired aerial
photo plane. You can do this yourself, if you're daring, from a firm
in Linden NJ. It costs $350 for a one-hour flight along your planned
itinerary. You take pictures thru extra flat windows in the side of
the plane or thru an open aperture in the floor.
The aerial views really bring out the geological shaping of the
land by the glaciers.
Some of the videos were accompanied by native sound or dubbed in
music. All were quite well done, the entire show being a blend of
several shoots.
Overtime
------
Lectures at SIBL run about one hour. but this one took an hour and
a half! Some people had to leave early, interrupting the projections
on the front screen. Most didn't mind the overtime and sat thru the
entire show, like I did.