GLACIERS AND LITHUANIA Danguolė Karmazienė It is a common knowledge today that the northern part of Lithuania including Lithuania was many times in

Transcription

1 GLACIERS AND LITHUANIA Danguolė Karmazienė It is a common knowledge today that the northern part of Lithuania including Lithuania was many times in Pleistocene years BP) covered by thick glaciers resembling the ones that today extend in Antarctica and Greenland, islands of ice seas and valleys of highlands. Encyclopaedias and geological dictionaries define a glacier as a large, slow moving river of ice, formed from compacted layers of snow on the Earth surface. Glaciers cover ~ 16.3 million km 2 or 11% of the land. The total volume of glacier equals to ~ 33 million km 3. They account for >3/4 of the fresh water resources of the Earth. Glacier covers of variable extent can be found in all continents except Australia. Glaciers develop in Polar Regions and high mountains above the snow boundary, i.e. in the areas where atmospheric discharges exceed the amount of melt or evaporated snow. Glacier ore composed of ice crystals formed as a result of compression and increasing density of snow cover. Permanent accumulating of sand and firn induce re-crystallization of compressed sand and formation of whitish firn ice. Due to high pressure, the density of lower layers increases and the firn ice crystallizes into glacial ice. The timeframe necessary for the snow cover to convert into ice may last from a few to a few thousand years. The thickness of glaciers slowly increases until they begin to move. Plastic flow is the main mode of continental glacier movement. The pressure in the lower part of the glacier where it is most plastic (in the centre, the thickness of the glacier may reach 2 3 or even 4.5 km in thickness) is the main driving force of movement. Under the impact of permanent weight of atmospheric discharges, the lower layers of glaciers soften and begin to flow radially (if there are no obstacles). At the edges, where glaciers are saturated with debris, the plastic flow slows down. Yet the pressure from the glacier centre does not reduce. In these cases, glaciers crack horizontally and flow as continuous and solid blocks. This mode of flowing is called movement within the internal crack planes. Due to their weight, glaciers flow to lower surface areas or spread to peripheries in plain areas. In mountain valleys, glacier flow like slow rivers. There are a few interrelated causes of glacier movement. The main are: 1 gravity, 2 regelation, i.e. periodical thawing and freezing of ice crystals due to pressure variations in the lower part of the glacier, 3 reduced friction due to melt water in the glacier bed, fringes, etc. Glaciers commonly are classified into two main groups: continental glaciers and mountain or alpine glaciers. The continental glaciers are further classified into glacier shields, glacier caps and plateau glaciers. The mountain glaciers are classified into mountain valleys, foothill, tidal, mountain care and suspended glaciers. Glacier covers shields occupy a special place among the continental glaciers and mountain and valley glaciers among alpine glaciers. The glacier covers are wide and thick and they cover vast areas of land, entire islands or almost entire continents (Antarctic). The glacier covers flow from their centres toward the peripheries. When glaciers descend to seas, icebergs break down

2 form the main ice mass. The glacier covers of Antarctic and Greenland account for >90% of the total glacier volume. The Antarctic glacier covers the entire continent except the Trans-Antarctic Mountains with summits towering above the glacier. The area of the Arctic glacier is >13 million. km 2, the thickness of glacier shield somewhere is >4 km (Wilkes Land 4776 m). The area of the Greenland glacier is 1.7 million. km 2, its average thickness reaches 1790 m and its maximal thickness is 3416 m. The mountain glaciers cover the mountain tops (a few neighbouring ones or a ridge). They descend till the snow line and lower. The largest mountain glaciers are represented by the ones in the Canada Arctic Archipelagos, Andes, Himalayas, and Jostendalbyrn in Norway (the largest glacier in Europe). The area of the latter is 487 km 2, the length 80 km and the thickness somewhere reaches >500 m. The valley glaciers flow in deep valleys from the mountain glaciers, glacier shields and glacier caps. The valley glaciers usually are long and descend below the snow line even to the sea level. Valley glaciers are found in many high mountains. Glaciers are moving slowly: from a few to about 100 m per year. In some parts of Antarctica, the rate of glacier movement is 1 10 m. The rate of movement depends on the glacier thickness, inclination and temperature. The highest rates of movement are characteristic of mountain glaciers. The movement rates of valley glaciers vary. It is highest in the glacier surface and slows down in the peripheries and close to the bed as a result of friction and debris load. Lithuania is a typical region of glacier activity in the nearest geological past. This is proved by traces in relief and sediment layers. They are firstly boulders: pinkish granites and blackish diabases, grey gneisses and pink sandstones, yellowish dolomites and white limestones. The native places of these boulders are in Sweden, Finland and Baltic Sea islands and bottom implying that the mentioned boulders were dragged to Lithuania. Secondly, huge blocks of ancient rocks originating in Lithuania and squeezed out from deeper layers. The size of blocks sometimes reaches tens and even hundreds of meters. The third group of glacier traces can be observed in outcrops containing muddled and corrugated once horizontally stratified layers. The fourth evidence of glacier activity is represented by till, i.e. dense and solid layers of sandy loams and loams containing boulders. The moving glacier eroded the rock surface and the tills of former glaciations on its way including the crushed debris into its mass. In the lower part of the glacier, the debris occupied up to 60 90% of the total glacier mass. Sediments of variable composition were deposited by melting ice in the peripheral parts of the glacier. The distribution of stones in the till and the structure and texture of sediments show the mode of glacier movement and conditions for till accumulation. The parallel incisions ( line-drawings ) and polished surfaces of solid bed rocks represent a n important evidence of glaciations. An expert investigating the Earth surface and its structure can easily distinguish between the hills formed at the glacier fringes or in cracks, plains formed by bay melt water and depressions generated by melting of ice blocks under the ground and

3 collapse of the earth surface. Geomorphologic and geological investigations of the Earth crust allow determining the size of glaciers, the boundaries of glaciations and the character of glacier recession. Comprehensive modern investigations of glacier activity results are very important for development of geological and geographical sciences. The evidences of sediment and relief origin are clearly visible in the environment of recent glaciers where the processes of ice melting, sedimentation and relief formation are in progress. This is an application of the so-called methodological actuality, i.e. cognition of past geological epochs based on investigations of recent processes. It should be emphasized that the evidences about the ancient glaciers were sought for and collected for almost one hundred years. The initial knowledge about the ancient glaciations was criticized. A controversy between glacialists (supporters of hypothesis of glaciations) and marinists (supporters of hypothesis of icebergs) set in. Even today, marinists of some countries adhere to their position: the greatest controversies occur in relation with the peripheries of Arctic basin where the earth surface and composing sediments might have been truly generated by water and icebergs. The youngest period of the Earth evolution is called: Quaternary, Ice Age or Anthropogene. The latter emphasizes the identity of intensive human evolution with the glacier epoch. The youngest period of the Earth evolution is undoubtedly marked by glaciation phenomena. These phenomena serve as a sufficient argument to refer to the Quaternary as the Ice Age. The Lithuanian glacial sediments developed in Pleistocene (during the last years) under the impact of repeated glacier advances from Fenoscandia. The glacier sediments cover the rocks of older geological systems as layers of different thickness. The thinnest layer (1 15 m) has occurred in North Lithuania as a result of exaration activity of glaciers. The thickness of Pleistocene deposits in the Žemaičiai and Baltija uplands reaches 314 m due to more intensive sedimentation and accumulation processes in the peripheral parts of the glaciers. Glacier deposits represent complicated systems called formations of glacier sediments. The sediments of the Quaternary system, formed mainly by Scandinavian continental glaciers, are investigated by researchers of Quaternary geology. Various research methods are applied in developing the surface and the underground parts of geological models. Outcrops in the steep river banks or slopes of quarries are most valuable sources of information. Most of Lithuanian outcrops expose only the youngest Quaternary sediments. The older geological layers are exposed only in North Lithuania. They are some kind of museum in the open for geologists. Another important source of geological information is contained in the structure of deeper sediments investigated by boreholes and geological sections. The last glaciation was the most important one for the formation of Lithuanian surface. Glacier tongues, a few hundred meters in thickness, advanced from the north and in a few thousand years covered almost the entire territory of Lithuania. The glacier stopped in South-East Lithuania. The region of longer pause of the glacier is referred to as the maximal spread limit of the last glacier.

4 The glacier of Lithuania melted years ago. Today glaciers are melting in Polar Regions and mountains. Their melting is a matter of concern for government, public and specialists. Therefore, it is not incidentally that the year is declared an international polar year Midler winters and frequenter dangerous phenomena in Lithuania an echo of polar processes Dr. Audronė Galvonaitė Head of Climatology Division Lithuanian Hydrometeorological Service under Ministry of Environmental a.galvonaite@meteo.lt Processes in Polar Regions have a profound influence on the global environment, and particularly on the weather and climate system. At the same time, the polar environment is impacted by processes at lower latitudes. The climate and weather in Lithuania as in other countries are depending on processes in arctic regions. Changes in climate. Due to climate and geographic features Lithuania falls into a group of countries vulnerable to climate change. The highest rate of temperature rise was registered in winter, whereas summer changes were insignificant. During the 19 th 20 th centuries the average annual air temperature in Lithuania increased by 0.7 C, the average temperature in the cold season by even 1.1 C. in the 20 th century a tendency for precipitation in cold seasons to increase and in summer to decrease was registered. Average climate peculiarities are determined by both continental and oceanic factors. Continental and maritime air mass exchange is interspersed by invasions of either artic or subtropical air, which cause short-term fluctuations of temperature and winds. Available date have enabled qualitative assessment of the change of climatic conditions in Lithuania over last years by their comparison to previous multi annual data (climatic normals): Mean air temperatures of late winter and spring seasons rose too (1.1 to 1.7 C) Hurricane winds frequency increased Droughty periods frequency increased Air temperature rise trend prevailed Number of days with minimal air temperature below 0 C decreased (by 8 12 d) Snow cover duration and depth decreased (especially in January February) Sunshine duration increased, especially in N-W and S-W regions Ice phenomena decreased and ice-break dates advanced

5 The climate in Lithuania is changing Petras Šinkūnas and Valentinas Baltrūnas, Institute of Geology and Geography GLOBAL CLIMATE CHANGE AND GLACIERS ABSTRACT The world s largest island Greenland due its ice covering is a natural laboratory to study the processes taking place during continental glaciations. The author of presentation took part in the geological expedition in Southwest Greenland in 2006 and 2007 and among other questions has been interested in ice dynamic features related to global climate change. To study features of till sedimentation in present glacial environments in order to identify them in till sequences of old continental glaciations is also very important along with the expediency of implication of the analysis method, when the knowledge on the present day processes is the key for the understanding of the past ones. Implication of such a method gained a possibility after the group of researches from Lithuania was supported by Lithuanian State Science and Studies Foundation (project C PALEOKLIMATAS ) to visit the Greenland ice sheet glaciers and to study the processes of sedimentation in present glacial environment. The ice in Greenland s ice sheet is irresistibly moving from the center towards the margin, however the faster and faster retreat of the ice sheet margin is observed during the last decades, causing a contraction of the ice sheet. This process is triggered by global climate change. The rate of ice melt in ice sheet margin at present is higher than of ice afflux from central regions. These processes are evident in Sermeq Kujalleq glacier at the eastern end of the Kangia fjord (Jakobshavn Icefjord) near Ilulissat and in Russell glacier near Kangerlussuaq. Very important information on climate and atmosphere composition change is preserved in the ice of continental ice sheet. The information on temperature, composition of gas of past atmosphere, eruption of volcanoes, etc. is acquired from the ice core. The ice core obtained from the boreholes is stored in the low temperature and analyzed in laboratories dating annual slice by slice. Hereby the continuous detailed information on the environment and its global change is documented for the last 25 thousand years covering the last glacial interglacial cycle. These studies have opened a new era in the research of palaeoenvironment and its changes. A short history of deep ice coring in Greenland is also presented in presentation Polar_year Talimaa Paleontological stratigraphical investigations in northern Eurasia in realization of IGC Programme Hab.dr. Valentina Karatajute-Talimaa. Institute of Geology and Geography, Vilnius, Lithuania Intensive search for remains of vertebrates in many key sections (Ordovician-Devonian deposits) of northern Eurasia have proved useful for regional, palaeocontinental or intercontinental geological (biostratigraphical, palaeoecological, palaeobiographical) correlation consequently, for correlation of marine\non marine deposits. In lithuanian palaentologists have take part in the geological expeditions in Spitsbergen (Norway), Timan-Pechora Province, Polar and North Urals, Severnaya Zemlya Archipelago, Taimyr Peninsula, Siberian platform (Russia). At present, several International Geological Correlation Programme (IGCP) endeavours cluster around climate change and desertification

6 Having succeeded in scaling Mt. Everest, I was sure I could climb any high peak but I saw no sense in collecting the mountains or trying to be first there. The idea, born a year later, gave a meaning to my further climbing expeditions: Why don t I take the flag that has flown over Everest to the highest peaks of the continents? This is how my quest with the motto The Lithuanian flag on the highest peaks of the continents! was born. The most unreal part of my Flag March was climbing the highest mountain in Antarctica. I knew more about the Amundsen and Scott expeditions to the South Pole than about the route to Vinson (4897 m). And where would the funds necessary to arrange the trip come from? In August 1994 I received a fax message from my Basque friend, Ramon, whom I had met a year before in the Himalayas. Ramon was going to climb Vinson in November and asked me to join him. It would be half the cost for two! he said, and I saw God s hand in it. In that time it was as difficult to prepare for this expedition as for Everest. I had to take care of everything myself. First of all I had to raise $15,000. I received my Chilean visa from the embassy in Moscow at the last minute. On the eve of my departure from Vilnius I had an accident and spent some time at a police station while they tried to establish whose fault it was. The moment I reached Punta Arenas in Chile I felt the breath of the icy continent. There, in the world of ice, cold and wind, behind the Strait of Magellan and Tierra del Fuégo, the five-kilometrehigh mountain awaited us. What we needed most of all on the way to the summit was patience. For five days and nights we waited for suitable weather for the plane to take us to Antarctica. During that time a Canadian Twin Otter aircraft crashed in a heavy gale. The crew perished in the burning plane. Lithuanian television covering the news announced that I had been to fly on this plane. We had to wait ten more days in Antarctica. When a snow storm prevented Ramon and I from leaving our tent we tried to eat and drink as little as possible. And not so much because of our depleted food stocks as to avoid having to go out into the arctic blizzard. Crevasses in the ice presented deadly danger. Covered with snow, they were difficult to notice. You could never know whether the snow would bear your weight or cave in, or how wide and deep they were. Because of that we walked tied to each other with rope: if one fell into a crevasse, the other had to stop the fall, and avoid falling himself. The higher we climbed the colder it became below -50 C. Once when Ramon tried to insert a film into his camera, it broke into pieces. However, the gale was worse than the severe cold. On the crest before lifting your foot you had to be sure the wind would not blow you off the mountain. In my Vinson diary I wrote: I cannot feel my hands. Is it frostbite? There s no way I can check: it s too cold to take off my gloves. I strike them against the ice axe and feel pain, which means they are all right. That day, besides the Lithuanian flag, the national flags of Latvia and Estonia flew on the top of the Antarctic: the neighbouring countries ambassadors to Lithuania had given me their flags. Despite the arctic climate, the Antarctic I remember will always be a white land of open spaces, blinding glaciers and rocks covered with hoarfrost, like hair going grey. We tried not to soil the pristine beauty. All waste we produced was put into special disposal bags we carried along with us (even body waste), which we brought back to Base Camp. From there the plane takes away all the waste together with the travellers from the white continent. Vladas Vitkauskas

7 Vladas Vitkauskas in Arctic