Tag Archives: ancient sand dunes

Mount Pisgah and the Hills of Martin County, Former Frances Langford Estate, SLR/IRL

Map of our area in the 1982 Coastal Management Zone document showing heights. in MC. (Mark Perry)
Map of our area in the 1982 Coastal Management Zone document showing heights. in MC. (Mark Perry)

Yesterday’s conversation regarding Sewall’s Point’s Mount Pisgah, at 57 feet, in the area of Frances Langford’s former estate got people talking about many things. One of the less controversial, but interesting was “heights.” My brother Todd wrote:

“Jacqui, with respect to Mt. Pisgah being the highest point, I think you are correctly specifying “along” the rivers (e.g. adjacent to the water). There are higher points listed in my video below. But all the ones on the waterfront are less than 37ft. The highest waterfront in Hobe Sound is 50ft and we ran US-1 over it!”

Mr Don Quazzo in his comments noted  the even higher heights than Mt Pisgah of the inland sand hills in the Skyline Drive area….interesting. Fascinating. Talk about history!

Today I will transcribe a piece of “Martin County’s 1982 Coastal Management Zone” shared with me years ago by Mr. Mark Perry. It talks about high places, ancient sand dunes, through out our county.

View Todd’s Time Capsule Flight video “The Hills of Sewall’s Point and Jensen Beach 1950 USGS Topo Map”:  (https://youtu.be/fIwsz5grVg0)

More detail of height in MC.
More detail of height in MC. Figure 3

Here we go:

The 1982 Coastal Zone Management Study of Hutchinson Island, Martin County, Florida, 1982, wa written by Florida Oceanographic Society and the Martin County Development Department.

Part II is entitled “Natural Geologic History.” It reads: “Just before the most recent Ice Age, the Wisconsin, which lasted from 100,000 to 11,000 years before present, the sea level was approximately 25-35 feet above the present mean seal level…At that time the sea was covering most of Martin County except for the Orlando Ridge, which was a narrow peninsula or series of islands and shoals, and the Green Ridge  which was an offshore bar with the crest at sea level…The sea beating against the much smaller Florida coast formed, by erosion and deposition, a broad terrace of Pamlico sands.

These sands were composed of mostly quartz, fossils and some carbon materials. The Atlantic Coastal Ridge was of pre-Pamlico origin was altered by an advancing Pamlico sea. This is evident by the south and north boundaries of the Jensen Beach and Jonathan Dickinson Sandhills which have spit-like structures projecting westward, as shown in Figure 3. (above)

The tall sandhills together with Sewall’s Point and Rocky Point form the backbone of the Atlantic Coastal Ridge. It is breached by the St Lucie River between Sewall’s Point and Rocky Point. During times of high sea level, like the Pamlico Period, the drainage basins of the St Lucie River and Loxahatchee River probably formed and ancient lagoon such as the Indian River Lagoon does today, with the older sandhills of Jensen Beach and Johnathan Dickinson acting as the barrier islands and dunes of that time. It was also during this time when Hutchinson and Jupiter Islands began forming as offshore bars….

—-Excerpt from MC 1982 Coastal Zone Management Study

Whether it is 100,000, 11,000, or 60 years ago, the more we know about the history and formation of Martin County the more likely we are to respect our natural resources.

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Blog post that elicited some discussion on heights and other things: (http://jacquithurlowlippisch.com/2016/01/21/scraped-and-pillaged-the-former-frances-langford-estate-slrirl/)