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Spatial reasoning is a critical skill in the Geosciences. Using a randomized control study with 592 undergraduate students enrolled in introductory and advanced Geology courses, our data indicates that regular, short interventions throughout an academic semester improve students' spatial thinking skills significantly with a moderate to large effect size when compared to an instruction-as-usual control group. We found evidence for additional gains in students who participated also in hands-on training interventions. We found even larger training effects on students who achieved correct scores of >50% on the practice modules, with gains of almost three-quarter of a standard deviation relative to their baseline scores. Male and female students display significant differences in spatial skills, with males outperforming females. Training resulted in similar magnitudes of improvement in both genders, so we see no evidence that the interventions closed the gender gap. Using the initial performance as a baseline, poor performers' spatial skills appear to improve through practice at the same rate as their peers. We argue that 15.4% of students improve their spatial skills through participation in the training towards a threshold that appears to be critical for participation in STEM careers. On a reflection survey, half of the students reported that they felt their spatial thinking skills improved through their participation, and over a third found the training beneficial for their overall learning in Geology or other classes. We hypothesise that formal training opportunities for spatial reasoning could increase the potential pool of students who successfully enter and succeed in Geoscience careers.

River morphology and dynamics are strongly influenced by active tectonics. We report channel dynamics for the Peikang River, which flows through the Hsuehshan Range in central Taiwan. Using a digital elevation model and field surveys, we constrain channel morphology for an ~90 km stretch of river to calculate unit stream power and boundary shear stress along the river path. Incision rates are estimated with optically stimulated luminescence dating of sand deposited on strath terraces. We find a strong correlation between unit stream power/ shear stress and incision rate, but only if variation in channel width is considered. A calibrated river incision rule implies river incision rates of ~9-13.5 mm/yr upstream of the Meiyuan and Tili faults and suggests that one or both of these structures are presently active. Our results indicate that the Shuilikeng fault is also actively deforming, as incision rates increase to ~6-10 mm/yr across it, compared to 1-4 mm/yr in adjacent reaches. Prominent narrowing across the Shuilikeng fault, and the absence of significant gradient variation indicate that channel width is a first-order morphological adjustment to differential incision. Only when the channel width-to-depth ratio reaches a minimum does the channel slope significantly adjust to local changes in base level, as is the case upstream of the Meiyuan and Tili faults. doi: 10.1130/B30035.1

Earthquakes and bedrock river incision are fundamental processes in the evolution of tectonically active landscapes, yet little work has focused on understanding how a bedrock river responds to a single large earthquake. Data from the 1999 [M.sub.w] = 7.6 Chi-Chi earthquake in central Taiwan show dramatic differences in river response that depend on the proximity to the rupture zone. Near the fault scarp, vertical ground deformation intensifies river incision on a time scale of years to decades, while distal to the fault, landslides induced by the earthquake mantle bedrock on the river bed with sediment, impeding incision for decades to centuries as the material is evacuated. This surprising spatial and temporal variability in bedrock incision caused by earthquakes has implications for the paleoseismic interpretation of bedrock terraces and for the evolution of tectonically active landscapes. doi: 10.1130/G30883.1

Analysis of emergent marine terraces in the San Joaquin Hills, California, and (super 230)Th dating of solitary corals from the lowest terraces reveal that the San Joaquin Hills have risen at a rate of 0.21-0.27 m/k.y, during the past 122 k.y. Movement on a blind thrust fault in the southern Los Angeles basin has uplifted the San Joaquin Hills and has the potential to generate an M(sub w) 7.3 earthquake within this densely populated area. Our structural modeling suggests that the fault dips to the southwest and slips at approximately 0.42-0.79 m/k.y., yielding an estimated minimum average recurrence interval of approximately 1650-3100 yr for moderate-sized earthquakes. Recognition of this blind thrust extends the known area of active blind thrusts and fault-related folding southward from Los Angeles into coastal Orange County.

Faulted alluvial fans and bajadas along the central Laguna Salada fault zone in northern Baja California record a recurrent history of oblique-slip Holocene earthquakes. Alluvial surfaces, which range from late Pleistocene to historic in age have been progressively displaced along the base of the crystalline rangefront, as well as along more basinward fault splays in alluvium. The recurrence interval determined from displaced alluvial deposits that are dated by soil profile development is in the range of 1-2 ka, with a corresponding right lateral slip rate of [approximately] 2-3 mm/yr, similar to that of the southern Elsinore fault in southern California. The most recent event along the fault zone is probably the widely felt earthquake of February 23, 1892. At least 22 km of the fault zone ruptured during this event, along both an oblique-dextral section of the northwest-striking Laguna Salada fault and the linked, northeast-striking Canon Rojo normal fault. The length of ground rupture and amount of displacement (4 m of dextral slip and 3.5 m of normal slip) suggest that the earthquake had a magnitude (Mw) of at least 7.1.

Five extensional fault systems were active between the mid-Eocene and the Halocene, and this development was due to the exhumation of metamorphic crustal rocks within the East Humboldt-Wood Hills, Nevada. High-angle normal faults in the metamorphic complex were found to have the youngest faults, which traverse existing extensional fault systems. Neogene and Quaternary extension in the East Humboldt-Wood Hills was due to the presence of high-angle normal faults in range fronts.

For long-term dual-chamber permanent pacing, atrial and ventricular lead stability is essential, in our overall experience with such pacing systems, four patients suffered cardiac arrest at a time distant from their pacemaker implantation. Since all four patients received prolonged closed chest cardiopulmonary resuscitation, we analyzed these events lo determine whether dual-chamber endocardial electrodes would remain stable in such traumatic conditions. Reliable atrial and ventricular lead position was confirmed at autopsy in three patients whose resuscitation attempts were unsuccessful and. in the fourth patient, by continued normal lead position and pacing function post-resuscitation. The keys to this stability include the use of lined atrial and ventricular endocardial leads and specific maneuvers at the time of implantation to verify fixation. Long-term stability of presently available endocardial leads in dual-chamber pacing systems can thus be anticipated. [ABSTRACT FROM AUTHOR]

We describe a case of a 79-year-old woman who developed pain and pitting edema of the upper right extremity due to total venous obstruction following the implantation of an atrioventricular sequential pacemaker. She was treated by arm elevation and anticoagulation after which the pain and edema subsided. To our knowledge, this is the first reported case of this complication occurring following implantation of a dual-chamber pacing system. We recommend that venographic studies be done after implantation if apparent arm swelling occurs, and that anticoagulant therapy be instituted if thrombosis is present. [ABSTRACT FROM AUTHOR]

Pseudotachylyte veins are solidified frictional melt generated by localized highstrain- rate deformation, and they are commonly considered to be reliable geological indicators of seismic slip. While originally thought to occur primarily in the upper crust, field studies suggest pseudotachylyte can also form far below the frictional-viscous transition. This implies a more complex inter play between brittle and crystal-plastic deformation in crustal-scale fault systems. We report a new example of deep pseudo tachylyte from the Paleoproterozoic granulite-facies strikeslip Cora Lake shear zone in northern Saskatchewan, Canada. Multiple generations of pseudotachylyte have been variably overprinted by plastic deformation and growth of high-grade metamorphic mineral assemblages (including garnet, ortho pyroxene, and/or clinopyroxene). Undeformed pseudotachylyte generation surfaces locally display sinistral offsets, and deformed pseudotachylyte shows unambiguous shear sense indicators compatible with left-lateral Cora Lake shear zone kinematics. The vein networks are commonly proximal to and inherit kinematically compatible semibrittle shear fractures. Thermobarometry and modeling of mineral stability fields for the overprinted pseudotachylyte suggest vein generation between 0.7 and 0.8 GPa and 700 °C and 800 °C (corresponding to depths from 24 to 28 km). Combined with the kinematic compatibility and the well-constrained regional exhumation history, this suggests that the Cora Lake pseudotachylyte formed contemporaneously with the waning stages of deformation in the shear zone and constitutes one of the deepest examples of fault-related pseudotachylyte yet reported in North America. Evidence exists for several possible formation mechanisms, including in situ generation via ductile shear heating--induced plastic instabilities, as well as from interaction with earthquakes nucleating in the overlying brittle fault system. All of these possible mechanisms ultimately suggest a more rheologically complex environment than might typically be expected for these lower-crustal pressure and temperature conditions. [ABSTRACT FROM AUTHOR]

The 4 April 2010 moment magnitude (Mw) 7.2 El Mayor-Cucapah earthquake revealed the existence of a previously unidentified fault system in Mexico that extends ∼120 km from the northern tip of the Gulf of California to the U.S.-Mexico border. The system strikes northwest and is composed of at least seven major faults linked by numerous smaller faults, making this one of the most complex surface ruptures ever documented along the Pacific-North America plate boundary. Rupture propagated bilaterally through three distinct kinematic and geomorphic domains. Southeast of the epicenter, a broad region of distributed fracturing, liquefaction, and discontinuous fault rupture was controlled by a buried, southwest-dipping, dextral-normal fault system that extends ∼53 km across the southern Colorado River delta. Northwest of the epicenter, the sense of vertical slip reverses as rupture propagated through multiple strands of an imbricate stack of eastdipping dextral-normal faults that extend ∼55 km through the Sierra Cucapah. However, some coseismic slip (10-30 cm) was partitioned onto the west-dipping Laguna Salada fault, which extends parallel to the main rupture and defines the western margin of the Sierra Cucapah. In the northernmost domain, rupture terminates on a series of several north-northeast-striking cross-faults with minor offset (<8 cm) that cut uplifted and folded sediments of the northern Colorado River delta in the Yuha Desert. In the Sierra Cucapah, primary rupture occurred on four major faults separated by one fault branch and two accommodation zones. The accommodation zones are distributed in a left-stepping en echelon geometry, such that rupture passed systematically to structurally lower faults. The structurally lowest fault that ruptured in this event is inclined as shallowly as ∼20°. Net surface offsets in the Sierra Cucapah average ∼200 cm, with some reaching 300-400 cm, and rupture kinematics vary greatly along strike. Nonetheless, instantaneous extension directions are consistently oriented ∼085° and the dominant slip direction is ∼310°, which is slightly (∼10°) more westerly than the expected azimuth of relative plate motion, but considerably more oblique to other nearby historical ruptures such as the 1992 Landers earthquake. Complex multifault ruptures are common in the central portion of the Pacific North American plate margin, which is affected by restraining bend tectonics, gravitational potential energy gradients, and the inherently three-dimensional strain of the transtensional and transpressional shear regimes that operate in this region. [ABSTRACT FROM AUTHOR]