Altötting county can be divided into three different landscapes. The "tertiäres Isar-Inn Hügelland" (hilly countryside beside the Rivers Isar and Inn, formed during the tertiary period) extends in the North, above the Inn Lowlands. Adjacent, the Inn Valley can be found, with an average width of ten kilometers. The South is characterized by moraine hills and the high terraces of the „Alzplatte“ and the beginnings of the foothills of the Alps.
Regarding the periods during which these different landscapes were formed, the region can be divided into the "tertiäres Isar-Inn Hügelland", and the landscapes in the middle and in the South of the county, which were both formed during the Ice Age.
The "tertiäres Isar-Inn Hügelland" is older, having been formed during the Younger Tertiary, the so-called Miocene, about 30 million years ago. The earth's activities that are responsible for shaping this landscape are directly connected with the upthrusting of the Alps. When the Alps raised, the sea was pushed away, filling the newly-formed basins in the North with salt water, which over time turned into freshwater.
The whole land between the Alps and the brim of the old low mountain ranges was covered with water. On the ground of that ocean, depositions accumulated, consisting for the most part of limy clay (marl and loam), mica, and fine-grained sand. In Altötting county, these deposits can be found in the form of fine and coarse sand, silt, and Alpine quartz rubble.
This rubble is partly cured in conglomerate. Beneath the rubble layers, watertight fine sands and clay were formed, preserving the largest groundwater deposit of the "tertiäres Isar-Inn Hügelland". Many farms still rely on their own wells to cover their water needs.