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Teaching methods that are often recommended to improve the learning environment in college science courses include cooperative learning, adding inquiry-based activities to traditional lectures, and engaging students in projects or investigations. Two questions often surround these efforts: 1) can these methods be used in large classes; and 2) how do we know that they are increasing student learning? At the University of Massachusetts, we have transformed the environment of a large-enrollment oceanography course (600 students) by modifying lectures to include cooperative learning via interactive in-class exercises and directed discussion. Assessments were redesigned as "two-stage" exams with a significant collaborative component. Results of student surveys, course evaluations, and exam performance demonstrate that learning of the subject under these conditions has improved. Student achievement shows measurable and statistically significant increases in information recall, analytical skills, and quantitative reasoning. There is evidence from both student surveys and student interview comments that for the majority of students, the course increased their interest in science -a difficult effect to achieve with this population.

Tertiary sediments around Lake Rudolf (now Lake Turkana) in the East African Rift Valley have yielded abundant palaeontological and palaeoanthropological remains. The present study provides a basis for interpreting the ancient lake environment and furthering our knowledge of rift valley lacustrine deposits. Bottom sediments in Lake Rudolf are fine‐grained (average 71% clay) well laminated and have montmorillonite, kaolinite and illite as the principal clay minerals. The sediments are relatively poor in silica (40–45%) but rich in Fe2O3 (10%). Both mineral proportions and chemical composition change systematically over the area of the lake and delineate four sedimentological provinces: (1) iron‐rich, silty kaolinitic muds (Omo Delta); (2) iron‐rich, fine‐grained montmorillonite muds (North Basin); (3) silty montmorillonite muds rich in Na2O and K2O (Central Delta); and (4) argillaceous calcite silts (South Basin). Omo Delta and North Basin sediments are derived from the volcanics of the Ethiopian plateau; the source of Central Delta sediments is the Precambrian metamorphic terrain of the rift valley margin; the South Basin has a restricted detrital input. The water in the lake is alkaline (pH 9.2) and moderately saline (TDS = 2500 p.p.m.). Comparisons with influent water from the Omo River indicate a 200‐fold concentration for the lake water. Models based on equilibrium between sediments and water column account for most of the non‐conservative chemical components in the lake water. Sedimentation rates are high (about 1 m per 1000 years) and the dominance of detrital sediments makes Lake Rudolf unusual in comparison with other closed‐basin lakes in the African Rift Valley although some similarities with ancient rift valley deposits are suggested.