Landsat scenes spanning 1978–2001 were used to classify thermokarst lake area and determine changes in lake coverage on the Tuktoyaktuk Peninsula in northwestern Canada. Changes in total lake area between scenes were substantial, spanning a 14% increase and 11% decrease, mostly owing to changes in the area of lakes >1.3 km2 in area. Increases in total lake area occurred primarily between 1978–1992, and decreases between 1992–2001. Differences in total lake area between scenes from different years depend strongly on cumulative precipitation in the 12 month period preceding scene acquisition (r2 = 0.82), and not on summer or mean annual air temperature (MAAT). Our results indicate that precipitation is the primary factor influencing the areal extent of lakes as detected by remote sensing. On the Tuktoyaktuk Peninsula, persistent lake area changes (if any) such as might occur by regional warming or changes in evaporation/precipitation balance over decades, are well‐masked by short‐term climatological changes.

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The map pattern of the Troodos ophiolite in Cyprus is an expression of a simple, elongate anticlinal structure. The crosssectional form of the anticline can be described by a sinusoidal dip model. On the northem flank of the anticline, the thickness of various units, number of gossans, etc., were measured along profiles, at 2.5 km intervals normal to strike, using existing maps supplemented by new observations. Profiles are approximately perpendicular to the spreading direction during crustal construction, and uncertainties in unit thickness are smaller than the range of unit thicknesses.Data on the profiles were analyzed quantitatively by harmonic analysis using the Fourier transform method. The harmonic analysis discloses cyclic variation in the thickness of major units, number of gossans, etc., that provides a link with the regular spacing of five groups of Cu -Fe -Zn orebodies. Groups of orebodies occur preferentially where sheeted dikes are at a shallow crustal depth, sheet and massive flows and dikes are common in the extrusives, the sediment-extrusive interface is at a relatively low elevation, and gossans and umbers are well developed. This association has the potential for providing an exploration tool in Cyprus and elsewhere. It can be accounted for in terms of the regular amval in the crust of batches of mantle-derived magma. Amval of a batch of magma in the crust would have been followed by voluminous sea-floor eruptions (which often formed sheet or massive rather than pillowed flows), rapid extension and subsidence, and enhanced hydrothermal circulation, a combination of circumstances leading to an increased probability of formation and preservation of orebodies.The thickness variations provide context for the few measured thickness values for in situ oceanic crust. The wide range in thickness values for the Cyprus ophiolite and the elevation of the sediment-extrusive interface suggest that the ophiolitic ocean crust was probably formed in a low-spreading-rate environment.L'ophiolite de Troodos, Chypre, apparait sur la carte gCologique comme une simple structure anticlinale allongee. La forme en coupe verticale de l'anticlinal reprksente un modkle de pendage sinusoial. Sur le flanc nord de l'anticlinal, les Cpaisseurs des differentes unites, des nombreux chapeaux fermgineux, etc., ont Ct6 mesurks le long de profils perpendiculaires 2i la direction, ?i des intervalles de 2,5 km, en utilisant les cartes existantes compl6tCes par de plus dcentes observations. Les profils sont quasi perpendiculaires h la direction d'extension dominante durant le stade de production de croiite ockanique, et les incertitudes h estimer l'epaisseur des unites sont moindres que la variation meme des 6paisseurs des unitCs.Les donnCes dCcoulant des profils ont Ct C traitees quantitativement par une analyse harmonique utilisant la mkthode de transform6e de Fourier. L'analyse harmonique divulgue une variation cyclique de l'6paisseur des principales unites, des nombreux chapeaux fermgineux, etc.; cette variation est aparentk avec ...

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