Lignite deposits of the Poznań rift valleys system as a guarantee of energy security for Poland

Current and future EU regulations are forcing Poland to reduce the participation of coal in the energy mix in 2030 and in the more distant perspective for the significant development of unsteady renewable sources. The stability of the Polish power system will still be based on lignite that is the cheapest source of energy in the country. This involves the exploitation of new deposits and construction of new power plants that will be useful as the reserve for renewable sources. The Poznań rift valleys system belongs to the richest lignite-bearing areas in Poland. In total, there are estimated over 7.8 billion tons of lignite possible to extraction. These deposits should be a gua­rantee of energy security for Poland.

2. The peopling of the earth

When did exploration begin and who were the first explorers? ‘The peopling of the earth ’ shows that the deep origins of exploration are inseparable from the long process of the peopling of the earth that began between one and two million years ago, with the migration of Homo erectus out of the East Africa rift valleys. It considers the Polynesian seafaring people whose remarkable exploratory oceanic migration resulted in settlements and cultural exchange around and across the Pacific Ocean. The maritime exploration of the Norse reached Iceland, Greenland, and Newfoundland. The global circle of humanity closed, and the first of history's two big stories, that of human divergence, ended, and the second, that of human convergence, began.

Crustal thickness and Moho sharpness beneath the Midcontinent rift from receiver functions

The Mesoproterozoic Midcontinent rift (MCR) in the central US is an approximately 2000 km long, 100 km wide structure from Kansas to Michigan. During the 20-40 million years of rifting, a thick (up to 20 km) layer of basaltic lava was deposited in the rift valleys. Quantifying the effects of the rifting and associated volcanic eruptions on the structure and composition of the crust and mantle beneath the MCR is important for the understanding of the evolution of continental lithosphere. In this study we measure the crustal thickness (H), and the sharpness of the Moho (R) at about 24 portable and permanent stations in Iowa, Kansas, and South Dakota by stacking Pto- S converted waves (PmS) and their multiples (PPmS and PSmS). Under the assumption that the crustal mean velocity in the study area is the same as the IASP91 earth model, we find a significantly thickened crust beneath the MCR of about 53 km. The crustal V_p/V_s ratios increases from about 1.80 off rift to as large as 1.95 within the rift, which corresponds to an increase of Poisson’s ratio from 0.28 to 0.32, suggesting a more mafic crust beneath the MCR. The R measurements are spatially variable and are relatively small in the vicinity of the MCR, indicating the disturbance of the original sharp Moho by the rifting and magmatic intrusion and volcanic eruption.