Why Are There So Many River Rocks In Our Yard?

We have a bit of a geological mystery on our hands… Everywhere we dig we find rather large round rocks – about the size of a basketball (+/-) and quite smooth…

Large smooth rocks

They’re in the back yard. They’re in the cellar (when we dug the trench for the new drain pipes). They seem to be everywhere. They look like river rocks – from a fairly large stream or a small river. But there’s no apparent sign of wetness.

We’ve seen townhouses in Harlem that have streams running under them (one in particular on 141st – on the edge of Hamilton Heights – across the street from the new location of Alexander Hamilton’s Grange) – but there’s no sign of a stream at our place.

So how did so many river rocks get on our property? Could these have been left by glaciers? Are they common in Harlem or in Manhattan in general?

2 thoughts on “Why Are There So Many River Rocks In Our Yard?

    • Noreen – I doubt they’re from the Harlem River – we’re roughly 3,000 ft away from the river.

      Yes, the Harlem River used to have a different course, but that was up at the tip of Manhattan – 5 miles away. There’s a section of what looks (on a map) like the Bronx which is actually part of Manhattan – Marble Hill. Once upon a time they were even allotted 212 phone numbers.

      I’ve heard there were streams all over Manhattan that are now gone, but those rocks look like they were from an awfully big stream. There’s just no evidence of an active stream, but perhaps one has been rerouted into the sewer as they’ve done elsewhere.

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