Tatra Mountains Valleys Carved by Rivers, Not Glaciers, Study Finds

The news in Polish

1. dolina  (f.)
   Obniżenie terenu między wzgórzami lub górami, często z rzeką na dnie. ↩︎
2. zlodowacenie  (n.)
   Okres w historii Ziemi, gdy duże obszary były pokryte lodem i lodowcami. ↩︎
3. lodowiec  (m.)
   Duża masa lodu, która powoli przesuwa się po powierzchni ziemi. ↩︎
4. osad  (m.)
   Materiały takie jak piasek, żwir lub muł, które zostały przeniesione i złożone przez wodę lub wiatr. ↩︎
5. jaskinia  (f.)
   Naturalna pustka lub otwór w skale lub pod ziemią. ↩︎
6. tworzyć
   Sprawiać, że coś powstaje lub istnieje; kształtować coś nowego. ↩︎

Translation

Text comprehension

Question 1: What percentage of the valleys’ depth already existed 1.6 million years ago?

Question 2: What did scientists study in order to make this discovery?

Vocabulary

Polish	English
dolina  (f.)	valley
zlodowacenie  (n.)	glaciation
lodowiec  (m.)	glacier
osad  (m.)	sediment
jaskinia  (f.)	cave
tworzyć	to create

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A new study has concluded that the deep valleys of the northern Tatra Mountains were largely formed by rivers millions of years before the region’s largest glaciations, challenging long-held assumptions about how the landscape came to look the way it does today.

Researchers found that around 80% of the current depth of the studied valleys already existed approximately 1.6 million years ago — before the most significant glacial periods in the Tatras. The valleys reach a total depth of around 700 metres. In the roughly 1.6 million years since, the main valleys of the northern Tatras deepened by only a further 100 to 200 metres, despite that period including the most intense glaciations.

The team arrived at these conclusions by analysing sediments preserved inside Tatra cave systems. Material carried underground by flowing water millions of years ago became sealed off from the surface, preserving a record that erosion had removed from the landscape above. Researchers examined 32 pairs of measurements of cosmogenic isotopes — aluminium-26 and beryllium-10 — in quartz-bearing sediments, obtaining 24 fully determined dates and six minimum-age estimates.

A key finding concerns the rate at which valleys deepened over time. Between approximately 2.2 and 1.6 million years ago, valleys were cutting into the ground at a rate of around 100 to 250 metres per million years. Over the last 800,000 years — the period of the greatest glaciations — that rate dropped to approximately 27 to 67 metres per million years. If glaciers had been the primary force deepening the valleys, researchers would have expected the rate to increase, not fall.

Dr Jacek Szczygieł, a scientist involved in the project, said this was strong evidence that glaciers were not responsible for the main work.