THE ICE AGE STOPPED HERE ---------------------- John Pazmino NYSkies Astronomy Inc www.nyskies.org firstname.lastname@example.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.