The Connecticut coast has submerged about 9.7 feet (3 meters) in the last 3500 years and about 27.5 feet (8.4 meters) in the last 8000 years. The submergence rate decreased to half an earlier rate about 3500 years ago, and salt marshes then filled the formerly open bays. Since their formation, the salt marshes have built upward to keep pace with continuing submergence. Vertical accretion on selected Connecticut tidal marshes has ranged between 1 and 16 mm per year between 1962 and 1966. Typical marshes are building upward at about 4 mm per year, which approximates the regional submergence rate for recent decades. Marsh edges have eroded unusually fast in recent decades, but only minor erosion was measured during detailed surveys between 1962 and 1966. (Author).