1. THE 2,500 METRE ISOBATH (CHAPTER 4)
Harald Brekke

2. The role of the 2,500 m isobath
The fixed points comprising the line of the outer limits of the continental shelf on the sea-bed, drawn in accordance with paragraph 4 (a) (i ) and (ii), either shall not exceed 350 nautical miles from the baselines ….. or shall not exceed 100 nautical miles from the 2,500 metre isobath, which is a line connecting the depth of 2,500 metres” (Paragraph 5, article 76)

3. Relevant bathymetric data
Primary data:
- Single-beam echo soundings - Multi-beam echo soundings
Complementary data:
- Bathymetric side-scan sonar measurements
- Interferometric side-scan sonar measurements
- Seismic reflection-derived bathymetric measurements
(See )
A classification of different geophysical data types that are relevant for the mapping and estimation of the thickness of marine sediments.

4. Ice-covered areas
In special cases such as in ice-covered areas the CLCS may regard also the following as primary data:
Seismic reflection-derived bathymetric measurements
Interferometric side-scan sonar measurements (See 4.2.3)

5. Selection of points along 2,500 m isobath for delineating the 100 M maximum limit
The 2,500 m isobath may occur as multiple repetitions along the continental margin
Use the first 2,500 m isobath from the baselines that conforms to the general configuration of the continental margin, unless there is evidence to the contrary (See 4.4.2)