THE Vulcanicity of the LAKE DISTRICT
I53 THE VULcANICITY OF THE LAKE DISTRICT. By J. FREDERICK N. GREEX. B.A., F.G.S. (Prtsid,.lial lltlelr...,. tI,U,o'red Ii" Ilh ~f.lf"y, 1919.) PLATES 9 TO I2. P.~GE I. INTROO\;CTlON J 53 II. EXPLOSION. • 155 III. EFF~SIO:'J. • 157 IV. TUFFS 165 V. ARRAKGEMEKT 168 VI. INTRUSION. • 174 VII.. SOLFATARIC 177 YIII. MOVEMEKT •• 180 IX. Col'iCLUSJOK 18I I. INTRODUCTION. OR some time past I have, as too rare opportunity offered, F been trying to sol\'e certain structural problems in the Lake District. For the most part this \\'ork has consisted in following certain geological lines across country, particularly the junctions of lavas and tuffs. This has involved or occasioned observations on the volcanic phenomena; and, as the district is readily accessible, of infinite variety, and of unequalled interest among British areas of igneous rocks, I have thought that a considera• tion of the vulcanicity, though as yet imperfectly kno\\'n, and some discussion of the light which it throws on igneous action generally, would be of interest to the Geologists' Associa• tion. The main strip of mixed intrusive and volcanic rocks covers a wild mountain area of over 400 square miles, containing such famous heights as Scawfell and Helvellyn, and surrounding wholly or partly the lakes of Ennerdale, Buttermere, Derwent• water, Ullswater, Thirlmere, \Vastwater, Haweswater, Devoke \Vater, Coniston, Grasmere, Rydal, ElterWater and Winder• mere, with many lesser tarns. Every part is easily visited; the exposures are magnificent and the existence of complex systems uf folding, intersected by deep valleys, enables the various horizons to be examined along numerous lines and some re• construction of their original form and extent to be attempted.
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