Vaheajad

Vaheajad is the plural form of a term used in Estonian geology and paleoclimatology to describe interglacial periods—the warm intervals between glaciations during Earth’s recent climate history. The singular form vaheaeg is commonly translated as interglacial. In scientific usage, vaheajad refer to extended periods when large ice sheets retreat, global average temperatures rise relative to surrounding glacial periods, and sea levels are higher than during glacials. These intervals are primarily situated within the Quaternary, especially the Pleistocene, and include the current Holocene epoch, which began about 11,700 years ago.

Clear evidence for vaheajad comes from multiple proxy records, such as oxygen isotope data from marine microfossils, pollen and plant remains in sediments, and ice-core chemistry. These records show characteristic shifts: reduced ice-volume, warmer temperatures, changes in biomes, and rising sea levels. The duration of vaheajad varies but is typically on the order of tens of thousands of years, with shorter fluctuations possible due to regional differences and local feedbacks.

Causes of vaheajad are linked to natural orbital variations—Milankovitch cycles—which regulate insolation (sunlight) patterns over tens of thousands of years, as well as feedbacks from atmospheric greenhouse gases like carbon dioxide and methane. The interaction of these factors drives the alternation between glacials and interglacials and shapes global and regional climate conditions.

In Estonian scientific discourse, vaheajad provide a convenient framework for discussing long-term climate variability, its drivers, and its impacts on environments and human history.