Lookbook · Natural heritage and karst landscapes

Cha Noi – Khe Gat Sinkhole
Cha Noi – Khe Gat

Beneath the forest canopy of Phong Nha – Ke Bang lies a geological feature reaching an estimated depth of 120 metres, with limestone cliffs and vegetation growing inside the sinkhole.

Source: Phong Nha – Ke Bang National Park Management Board · Photograph supplied by the researcher

01 / The field survey story

A hidden depression in the heart of the forest

A karst sinkhole was recorded in the Cha Noi – Khe Gat area. Its opening is approximately oval, its limestone walls are irregular, and the space below widens. The principal field survey took place in July 2025; the findings were published by the Phong Nha – Ke Bang National Park Management Board on 23 October 2026.

100–120 mEstimated depth

2.18 haPreliminary opening area

190 × 140 mOpening dimensions

250 × 200 mEstimated lower chamber dimensions

02 / Views from the field

Original unlabelled aerial photograph of the Cha Noi – Khe Gat sinkhole

An aerial view of the forest sinkhole

View from above

A deep depression breaks the otherwise continuous forest canopy, with exposed limestone visible along its rim. This is a field photograph showing the actual landscape, not a reconstruction.

Source: Phong Nha – Ke Bang National Park Management Board; photograph supplied by the researcher.

Aerial image of the Cha Noi – Khe Gat sinkhole opening and limestone cliffs

The shape of the sinkhole opening

Drone photography · Karst landscape

From above, the opening has an irregular outline amid the tree canopy. Pale limestone outcrops contrast sharply with the surrounding green vegetation.

Photograph: Jungle Boss · Materials: Phong Nha – Ke Bang National Park Management Board. View original image

Rugged limestone walls and forest canopy inside the Cha Noi sinkhole

Limestone cliffs and forest canopy

Inside the sinkhole

The rugged limestone walls feature ledges and weathered recesses, while trees grow along the foot of the cliffs. The photograph provides a visual reference for assessing a conceptual cross-section of the sinkhole.

Photograph: Jungle Boss · Materials: Phong Nha – Ke Bang National Park Management Board. View original image

Field photographs of plants and snail shells recorded during the sinkhole survey

Traces of biological life

The field photographs document plants and snail shells within the survey area. These are preliminary biological observations; they are not sufficient to identify species composition or establish the structure of the ecosystem.

Photograph: Jungle Boss · Materials: Phong Nha – Ke Bang National Park Management Board. View original image

“A sinkhole is more than a void in limestone: it raises questions about geomorphological history, local microclimates and the development of living communities.”

03 / Location and scientific data

VietGreenGIS screenshot showing the provisional sinkhole location on satellite imagery and its attribute panel

Locating the sinkhole on satellite imagery

A VietGreenGIS screenshot shows the provisional sinkhole point against satellite imagery, together with an information panel and coordinates reported in VN-2000 as X = 512888, Y = 1946080

GIS visualisation: VietGreenGIS · Provisional reference-point data; source material from Phong Nha – Ke Bang National Park.

VietGreenGIS screenshot showing terrain and environmental indicators for the area surrounding the sinkhole

Terrain and survey-area indicators

The VietGreenGIS analysis summarises the study-area extent, elevation from the GLO-90 digital elevation model and environmental indicators used to characterise the natural setting around the sinkhole.

GIS visualisation: VietGreenGIS · Copernicus DEM GLO-90; figures relate to the wider survey area, not solely to the sinkhole floor.

Environmental landscape

Study area: approximately 1,430 ha

Vegetation index (NDVI)0.856

Strong vegetation signal in valid samples · Sentinel-2 L2A, 1 October 2026

Tree cover99.9%

Dominant among the classified land-cover categories · ESA WorldCover 2021

Mean elevation591 m

Marked relief variation across the study area · Copernicus DEM GLO-90

Scientific note: The VietGreenGIS indicators describe a wider survey area of approximately 1,430 ha, not just the 2.18 ha sinkhole opening. High NDVI and tree-cover values do not establish that the forest is primary or old-growth. The coordinates and sinkhole boundary still require verification in the field.