Exploration of the earth and core samples

A core sample is a column of rock or sediment taken from a borehole by a specially designed drilling method. The core sample is an important source of geological information that provides information on the rocks and sediments in the earth. The properties of the rock layers (mineral and chemical composition, structure, etc.), their sequence, thickness, age, etc. are determined on the basis of the core sample [1, 2].

In Estonia, drilling boreholes began in the nineteenth century, initially mostly for the purpose of creating wells. In the early twentieth century, people also started taking core samples in connection with oil shale and phosphate rock research. The oldest surviving core samples in Estonia are taken from the 505-metre and 721-metre boreholes drilled in the Jõhvi magnetic anomaly area in 1937–1938. In the 1950s, tens of thousands of boreholes were drilled in Virumaa in the course of the research on oil shale and phosphate rock. During the heyday of geological research in 1960–1985, up to 30 kilometres of boreholes were drilled in a year. In recent decades, only a kilometre of core samples per year have been drilled [3]. The longest core sample in Estonia is 815.2 m long and originates from the Soovälja borehole in Hiiu County, drilled in the centre of the Kärdla meteorite crater in 1990 [2].

While Northern Estonia has been well researched, much of the South Estonian earth is still waiting for scientists to explore it.

State-owned core samples (145,000 m in total) are stored in depositories in Arbavere (Lääne-Viru County), Keila and Tuula (Harju County), Särghaua (Pärnu County), and Turja (Saare County) [4]. The storage of core samples allows for them to be used in the performance of new geological tasks, i.e. the cost of planned geological works (geological mapping, hydrogeology, exploration of mineral resources) decreases and the reliability of exploration of the geological structure of the Estonian earth increases.

Last modified: 30.11.2021

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[1] Rammul, Ü. Niitlaan, E. Reinsalu, E. Keerberg, L. (koostajad). 2017. Ehitusmaavarade uuringu- ja kaevandamisalade korrastamise käsiraamat. OÜ Inseneribüroo Steiger https://www.digar.ee/viewer/et/nlib-digar:332505/292132/page/1

[2] Eesti Geoloogia Seltsi veebileht http://www.egeos.ee/egeos/geoteave/puursudamikud/

[3] Eesti põuest pool (p)uurimata. Loodusesõber 3/2012 - http://vana.loodusajakiri.ee/loodus/artikkel2071_2046.html

[4] Eesti Geoloogia Seltsi veebileht http://www.egeos.ee/egeos/geoteave/puursudamikud/