Every outline on this map is a real shoreline: U.S. Coast Survey maps from 1848, later federal surveys digitized by the Mississippi Office of Geology, and four decades of Landsat imagery processed by the USGS. Between the first survey and the 1986 shoreline, Ship Island shrank from 601 to 374 hectares and Petit Bois from 814 to 537. Katrina tore Ship apart in 2005, and the 2025 satellite frame shows it rebuilt. Press play.
Bar = share of each island's first measured area remaining. Survey and Landsat figures use different shoreline definitions, so compare within one source.
Hectares (1 ha ≈ 2.47 acres). Dots: survey shorelines traced for this map. Thin lines: Landsat. Landsat counts wet beach at 30 m resolution and reads about 10–15% higher than surveys of the same year, so the jump in the 1980s is a change of method, not new land.
Prevailing southeast winds push waves and currents west along the Gulf beaches. On the map, watch the eastern ends of Petit Bois and Horn erode while their western tips stretch out. Petit Bois in 1848 reached far to the east of where it sits today.
Big hurricanes push surge over the islands and slice the narrowest segments in two. The 1966 and 1986 surveys show Ship Island in pieces, and the Landsat frame from the fall of 2005 shows how little of it survived Katrina.
Ship channels to Mobile, Pascagoula and Gulfport were dredged ever deeper across the sand bars between the islands. USGS geologist Robert Morton found that land loss sped up on every island in step with that deepening, because the channels trap sand that would have fed the next island downdrift.
1848–1986: historical shorelines digitized by the Mississippi Office of Geology from Coast Survey and NOAA topographic sheets (1848–50, 1916–17, 1950, 1966, 1986). I joined the shoreline segments into island polygons. The areas come out within a few percent of Morton's published USGS figures. The 1966 set covers only Cat and Ship.
1987–2025: Landsat. Horn, Petit Bois and Dauphin use the USGS island outlines extracted from Landsat (1984–2015), one median scene per year plus scenes before and after Katrina. Cat and Ship use the USGS 1984–2025 land-fraction rasters, combined into yearly composites and outlined where land covers at least half of each 30 m pixel. Horn, Petit Bois and Dauphin hold their 2015 outlines after that.
Between survey dates the map cross-fades from one real outline to the next; it does not invent the shapes in between. The drifting-sand particles are an illustration. The context coastline is from the GSHHG database.
Hurricanes: every track and intensity is NOAA's HURDAT2 best-track record, interpolated between its six-hourly fixes; the map includes each hurricane whose recorded center passed within about 150 km of the islands since 1851, plus Betsy. Storms are drawn to scale. The dashed ring is the radius of hurricane-force winds, taken from the record from 2004 on and estimated from intensity before that, using a standard wind-profile relationship (Willoughby and Rahn, 2004). Stronger storms spin faster, show a clearer eye, and tint the Sound more deeply. Cloud patterns are illustrations, and records before about 1900 are less certain.
Look closely: a few period vessels and residents of the Sound are tucked into the chart in the years they belong. Hover or tap them.