Sökning: "craters"

Visar resultat 1 - 5 av 18 avhandlingar innehållade ordet craters.

  1. 1. Cold-climate landforms on Mars and Earth-analogues in Svalbard

    Författare :Andreas Johnsson; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mars; Svalbard; Spitsbergen; periglacial; ice; permafrost; Earth-analogues; terrestrial analogues; geomorphology; landforms; solifluction; debris flow; gully; craters; cold-climate;

    Sammanfattning : Periglacial landforms on Earth reflect cold-climate conditions and are intimately related to processes due to the presence of ground ice and perennially frozen ground, permafrost. The overall objective of this thesis is to investigate the potential of Svalbard as an analogue to Mars cold-climate landforms, and explore past and present processes and surface conditions on Mars by inference from morphological counterparts in Svalbard. LÄS MER

  3. 2. The micrometeorite flux to Earth through the Phanerozoic Eon : Reconstructed using sediment-dispersed extraterrestrial spinels

    Författare :Ellinor Martin; Kärnfysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; chromite; chrome spinel; micrometeorites; Phanerozoic; asteroid breakup; ordinary chondrites; 3He anomalies; lunar impacts; ice age; impact craters; zircons;

    Sammanfattning : The purpose of this thesis is to add an astronomical component to the history and evolution of Earth by reconstructing the micrometeorite flux to Earth at different time intervals during the Phanerozoic Eon, using sediment-dispersed extraterrestrial spinel group minerals as a proxy. Chromite and chrome spinel are common refractory members of the spinel group, occurring in both extraterrestrial and terrestrial rocks. LÄS MER

  4. 3. Late Ordovician Faunal Distribution and Ecospace Partitioning in Marine Impact Craters : The Aftermath of the Lockne and Tvären Events

    Författare :Åsa M Frisk; Lars Holmer; Jan Ove Ebbestad; Maurits Lindström; Alan Owen; Uppsala universitet; []
    Nyckelord :impact crater; Lockne; Tvären; ecospace; the Great Ordovician Biodiversification Event; NATURAL SCIENCES; NATURVETENSKAP;

    Sammanfattning : In the Middle to Late Ordovician a boost of marine biodiversity occurred which is regarded as the most rapid diversity in Earth’s history, and termed the Great Ordovician Biodiversification Event. This time is also unique in that at least four marine meteorite craters with a good record of post-impact sediments are preserved in Baltoscandia. LÄS MER

  5. 4. Investigation of the correlation of fracture frequency and electric resistivity in impact craters in crystalline rocks

    Författare :Ann Bäckström; KTH; []
    Nyckelord :Electric resistivity; Fracture frequency; Impact generated fractures; Electro-magnetic techniques; VLF-R method; MT method; Window-mapping technique; Three-dimensional fracture calculations; heat-exchange structure; geothermal energy;

    Sammanfattning : Impact craters are formed when a large meteorite or comethits the Earth. At the impact a shock wave is released causingabundant fracturing in the surrounding bedrock. This type offracturing is intense and occurs throughout a very large volume(>100 km3) of the bedrock. LÄS MER

  7. 5. Post-impact sediments in the Lockne and Tvären craters, Sweden: facies distribution and gastropod-like molluscs

    Författare :Åsa Frisk; Uppsala universitet; []
    Nyckelord :;

    Sammanfattning : .... LÄS MER