The son of Alonso de Cárdenas y doña Elvira de Figueroa and Maria García Osorio, Garcia Lopez de Cardenas was the comendador de Caravaca.
Cardenas was a conquistador attached to the exploits of Francisco Vasquez de Coronado. Expeditions, including one led by Pedro de Tobar, had heard reports of a large river north of Cíbola (Zuñi). Cárdenas was dispatched in 1540 by the general stationed in Cíbola with the express mission of locating such a river and returning within 80 days. Pedro de Sotomayor accompanied him to record the event as a cronista. After some twenty days of marching in a northerly direction, he was successful; but his band found difficulties in reaching the river (called the River Tizon), owing to the sheer vertical distance down from their position. They were standing on the South Rim, a great canyon. After several days of failed attempts to descend to the water (his men were suffering from thirst), his party was forced to return to Cíbola.
While Cardenas is credited with being the first European to lay eyes on the Grand Canyon, Hernando de Alarcón had explored the Colorado River several months beforehand.
Before the army left Culiacan, Hernando de Alarcon was sent in command of a naval expedition to explore the coast and to co-operate with the land expedition.
Don Pedro de Tovar, with seventeen horsemen and three or four foot soldiers, was sent out by Coronado to explore these villages, and entered the country quietly, arriving after nightfall and concealing themselves on the edge of the village.
On their return Cardenas and his companions saw some water falling over a rock, and learned from the guides that some bunches of crystals which were hanging there were salt, of which they gathered a quantity and brought it back to Cibola, dividing it among those who were there.