The body of water known under the name of “East River” (or once also known under the name of “Sound River”), is not an actual river at all. By definition, a river flow from inland fresh water source, such as mountain runoff or spring. Or, the East River is rather a narrow, navigable channel of salted water, connected on both ends to the Atlantic Ocean. It connects Upper New York Bay on its south end to Long Island Sound on its north end and it separates Long Island (including the boroughs of Queens and Brooklyn) from the island of Manhattan and the Bronx on the North American mainland. Therefore, by definition, it is a marine tidal strait. Because of tides, it appears to flow like a river.
The East River is 16 miles (26 kilometers) long and from 600 to 4000 feet (183 to 1 219 meters) wide.
The physical environment of New York City and its surroundings reflects the culmination of geologic processes affecting the North American continent for more a billion year period. Highlights of this geologic story include the formation and the destruction of ancient mountain ranges and seaways created by the shifting and colliding of ancient land masses. This area is primarily composed of sediments that were metamorphosed during the Taconic and Acadian orogenies around 500 to 400 million years ago. Garnets can be found in the rocks of Hartland Formation and Manhattan Schist and it is in these hard rocks that the city skyscrapers have their foundation. More recently, in geological terms (Pleistocene epoch or “Ice Age”: from 1.8 million years ago to 8 000 years ago), there were episodes of continental glaciation when ice sheet spread southward from eastern Canada into this area of USA. Around 17 000 years ago, the part of Wisconsin glacier covering the New York City was about 985 feet (300 meters) thick. Much of the modern landscape owes its character to the sculpting forces of glacial ice and the erosion by rivers south of the ice front. Between 17 000 years ago to 11 000 years ago, large ice sheets bulldozed the landscape. Rocks with the glaciers scrapped and scratched the bedrock of Central Park, producing long linear striations and grooves. Long Island is composed of rubble (glacial till or moraine) that glacier left behind as it melted. In this period, around 11 000 years ago, the channel of East River was formed by the retreating/melting of the glacier and advancing of the Atlantic Ocean. According to one source, the difference in the shape of the channel between its lover (southern) and its upper (northern) portions is the best evidence of the glacial activity. The upper portion (from Long Island Sound to Ward’s Island) is wide, meandering, and has deep narrow bays on the both banks, scoured out by the glacier’s movement. This portion runs largely perpendicular to the glacial motion. The lover portion (from Ward’s Island to New York Bay) is narrower, with straight banks. This portion runs north-south, parallel to the glacial motion. From the formation of the channel, it took at least another 5 000 years, before the area found the aspect similar to the one we know today.
Ever since its discovery by Europeans, tides and strait’s naturally narrow channel, have caused problems for generations of sailors. Especially the passage located at its midpoint (along the east of Ward’s Island) called the Hell Gate. It wasn’t until 1885, that its last dangerous rocky reefs were cleared out by the largest (non atomic) explosion caused intentionally by man. But the strait still posses challenges. Its swift current, with water moving as fast as four knots, can be dangerous to those who underestimate it.
The strait is joined in its northern section by the Bronx River. North of Ward’s Island, it is joined by the Bronx Kill. On the south side of Ward’s Island, it is joined by another strait: the Harlem River. It is also via Harlem River and Spuyten Duyvil Creek, that the strait connects with the Hudson River. On Long Island, Newtown Creek drains into the strait, forming part of the boundary between Brooklyn and Queens. The strait contains several islands in its upper and lower sections. It is spanned by eight bridges and thirteen tunnels.
Historically, after the establishment of Europeans in the area, the lower portion of the strait was one of the busiest and most important channels in the world, particularly during the first three centuries of the New York City history. The first bridge to span the strait was the Brooklyn Bridge. Opened in 1883, it had replaced frequent ferry services.
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