He began his second South American expedition on March 30, 1801, in Cartagena, Colombia. From Barancas Nuevas he set out upstream on the Magdalena River with his colleague Bonpland. When they reached Honda, eight rowers died of disease. After four days of steep ascent, they reached the Andean plateau. Along the way, Humboldt reconnoitered the Colombian silver mines and gold production for the Spanish viceroy. They continued their way through the dense forests between the swamps, making their way through the narrow gorges. He wrote, “Everywhere we found the bones of animals that had died of cold and exhaustion.”
In Ecuador, they explored volcanoes, some climbed at first, but some peaks caused a lot of trouble, with the fact that they survived a strong earthquake. And then on June 23, 1802. managed at about 6000 m to the volcano Chimborazo, almost to the top. For the next 30 years, that height remained a world record. It was then that Humboldt was the first in the world to describe the symptoms of altitude sickness: dizziness, vomiting, bleeding from the lips and gums. This was the first description of the symptoms of altitude sickness. They quickly descended to the upper reaches of the Maranon River and the Inca cities near Cajamarca. Measurements showed that they crossed the magnetic equator.
Along the way, Humboldt recorded everything in detail – flora and fauna, planetary movements, archeological sites… After the fourth crossing of the Andes, they arrived in Lima, the Peruvian capital, in October 1802. This ended the second successful expedition to South America.