At the University of Bergen, Andersen played a central role in building up the study of Quaternary geology.
His students and the university benefited from his international contacts and he conducted filed trips to the Antarctic, South America and New Zealand.
Most of all his contribution was to reveal the foundation of Scandinavian landscapes.

Andersen's first expedition to the South Pole came in a period of small Norwegian interest in the Antarctic after the great achievements of Roald Amundsen in 1911–1912.
Andersen was the second Norwegian to visit the Pole after the Amundsen expedition.
An American expedition which reached the Pole a week before him honored his achievements by naming a mountain escarpment Andersen Escarpment after him.

During the fieldworks for his Master's thesis "Om isens tilbaketrekking i området mellom Lysefjorden og Jøsenfjorden i Ryfylke" (On the glacial retreat in the area between the Lysefjorden and Jøsenfjorden in Ryfylke), with Werner Werenskiold as advisor, he found among other things that Trollgaren was a moraine, and that it was formed in the early Holocene, probably about 11,000 years ago.
Here he met his youth curiosity.
Andersen broke new ground both methodologically and theoretically with this work.
He developed a method for stereoscopic analysis of aerial photos in the assessment of moraines.
During the 1950s and 1960s he assessed the moraines in most of Norway, from Lindesnes to Troms.
The assessment of the moraines of Jæren and the rest of the south coast of Norway was the basis of his PhD thesis "Sørlandet i sen- og postglacial tid" (The Norwegian South Coast in late and postglacial time), under guidance of Olaf Holtedahl, defended in 1960.

Andersen discovered an until then unknown area of Rogaland containing rock of the Cambrian-Silurian age on a much lower level than the surrounding bedrock.
His collected fossiles from this area were deposited in the Paleontologic Museum at Tøyen in Oslo.
In this material Professor Gunnar Henningsmoen discovered an until then unknown trilobite species, which was given the name (Ptychparia anderseni) for Andersen.
During this fieldwork in the Lysefjord area, Andersen developed a method for determination of climatic conditions from the reconstruction of Ice Age glaciers which is still used by geologists and geographers.

Andersen's first paper  is one of the most basic papers in Norwegian glacial geology, even though it was published before C-14 dating was available.
The Younger Dryas glacier of the Lysefjord was reconstructed in three dimensions and compared with the glaciers in Greenland today.
Further, the highest side moraines were used to determine the equilibrium line of the paleo-glaciers and thus its lowering by comparison with today's glaciers.
In this way he was able to estimate the decrease of summer temperature with surprising accuracy.
These decreased temperatures were in compliance with the findings of botanist Knut Fægri at the Younger Dryas glacier of Jæren.
At the University of Bergen, Andersen played a central role in building up the study of Quaternary geology. His students and the university benefited from his international contacts and he conducted filed trips to the Antarctic, South America and New Zealand. Most of all his contribution was to reveal the foundation of Scandinavian landscapes.
Andersen's first expedition to the South Pole came in a period of small Norwegian interest in the Antarctic after the great achievements of Roald Amundsen in 1911–1912. Andersen was the second Norwegian to visit the Pole after the Amundsen expedition. An American expedition which reached the Pole a week before him honored his achievements by naming a mountain escarpment Andersen Escarpment after him.
During the fieldworks for his Master's thesis "Om isens tilbaketrekking i området mellom Lysefjorden og Jøsenfjorden i Ryfylke" (On the glacial retreat in the area between the Lysefjorden and Jøsenfjorden in Ryfylke), with Werner Werenskiold as advisor, he found among other things that Trollgaren was a moraine, and that it was formed in the early Holocene, probably about 11,000 years ago. Here he met his youth curiosity. Andersen broke new ground both methodologically and theoretically with this work. He developed a method for stereoscopic analysis of aerial photos in the assessment of moraines. During the 1950s and 1960s he assessed the moraines in most of Norway, from Lindesnes to Troms. The assessment of the moraines of Jæren and the rest of the south coast of Norway was the basis of his PhD thesis "Sørlandet i sen- og postglacial tid" (The Norwegian South Coast in late and postglacial time), under guidance of Olaf Holtedahl, defended in 1960.
Andersen discovered an until then unknown area of Rogaland containing rock of the Cambrian-Silurian age on a much lower level than the surrounding bedrock. His collected fossiles from this area were deposited in the Paleontologic Museum at Tøyen in Oslo. In this material Professor Gunnar Henningsmoen discovered an until then unknown trilobite species, which was given the name (Ptychparia anderseni) for Andersen. During this fieldwork in the Lysefjord area, Andersen developed a method for determination of climatic conditions from the reconstruction of Ice Age glaciers which is still used by geologists and geographers.
Andersen's first paper  is one of the most basic papers in Norwegian glacial geology, even though it was published before C-14 dating was available. The Younger Dryas glacier of the Lysefjord was reconstructed in three dimensions and compared with the glaciers in Greenland today. Further, the highest side moraines were used to determine the equilibrium line of the paleo-glaciers and thus its lowering by comparison with today's glaciers. In this way he was able to estimate the decrease of summer temperature with surprising accuracy. These decreased temperatures were in compliance with the findings of botanist Knut Fægri at the Younger Dryas glacier of Jæren.
Bjørn G. Andersen