The creation of fractures in bedrock dictates water movement through the critical zone, controlling weathering, vadose zone water storage, and groundwater recharge. However, quantifying connections between fracturing, water flow, and chemical weathering remains challenging because of limited access to the deep critical zone. Here we overcome this challenge by coupling measurements from borehole drilling, groundwater monitoring, and seismic refraction surveys in the central California Coast Range. Our results show that the subsurface is highly fractured, which may be driven by the regional geologic and tectonic setting. The pervasively fractured rock facilitates infiltration of meteoric water down to a water table that aligns with oxidation in exhumed rock cores and is coincident with the adjacent intermittent first-order stream channel. This work highlights the need to incorporate deep water flow and weathering due to pervasive fracturing into models of catchment water balances and critical zone weathering, especially in tectonically active landscapes. The creation of fractures in bedrock facilitates water movement through the subsurface which breaks down rock creating porous soil and weathered bedrock. Water movement is vital for important processes like plant growth, streamflow, and groundwater recharge. However, understanding how fracturing, water flow, and rock weathering interact is challenging because the subsurface is difficult and expensive to measure. Here we use observations from drilling, water level monitoring, and geophysics to understand these interactions. Our results indicate that the subsurface is highly fractured due to the geologic and tectonic setting. The large number of fractures makes it easier for water to flow through the subsurface and causes chemical alteration of bedrock. This may cause water to flow outside of the catchment through the subsurface. This work highlights the role of geologic and tectonic processes in driving fracturing, which dictates the movement of water and subsurface weathering beneath Earth's surface. Deep weathering may be due to enhanced permeability and surface area from inherited rock damage from local geologic and tectonic conditions Weathering and water flow extend to the elevation of the adjacent first-order intermittent stream channel The deep weathering and fracturing front may allow for inter-basin water flow in headwater catchments

Strike-slip faults on Europa may slide back and forth in response to diurnal tidal stresses, which could generate significant frictional heating near the surface. Previous shear heating models assumed fault sliding rates a priori, without showing how the sliding rate is connected to the resolved stresses acting on the fault. Here, I calculate the cyclic displacement along tidally driven faults. I use a Mohr-Coulomb failure criterion to determine the frictional failure depth, which varies throughout the tidal cycle. The displacement on the fault is calculated assuming an elastic broken plate model. The magnitude of cyclic displacements along a fault depends upon the coefficient of friction and the shear modulus of the ice shell. If Europa's ice shell is weak, diurnal tidal stress can cause faults on Europa to slide back and forth by similar to 0.1 to 2 m each cycle. Such large amounts of cyclic slip may be enough to frictionally heat the ice and potentially produce near-surface melting. If Europa's ice shell has the strength of intact ice, faults become less responsive to cyclic tidal stresses and would only slide 0.01 to 0.2 m per cycle. Plain Language Summary Europa, Jupiter's icy moon, has many fractures and faults in its ice shell. As the moon gets stretched and squeezed by tidal forces from Jupiter, faults may slide back and forth, generating a significant amount of shear heating. I show that tidal stresses can cause faults to slide back and forth by up to 2 m each orbit. In some cases, frictional heating can cause faults to slide fast enough to generate near-surface melting and potentially water pockets only a few 100 m below the surface.

Alluvial fans in southern Monglia occur along a group of narrow discontinuous mountain ranges which formed as transpressional uplifts along a series of strike-slip faults. They provide information on the nature of neotectonic activity in the eastern Gobi Altai range acid on palaeoclimate change. Alluvial fan formation was dominated by various geomorphological processes largely controlled by climatic changes related to an increase in aridity throughout late Quaternary times. Their sedimentology shows that initially they experienced humid conditions, when the sedimentary environments were dominated by perennial streams, followed by a period of increasing aridity, during which coarse fanglomerates were deposited in alluvial fans by ephemerial streams and active-layer structures were produced by permafrost within the alluvial fan sediments. With climatic amelioration during early Holocene times, the permafrost degraded and fan incision and entrenchment dominated. Sedimentation was then confined to the upper reaches of the fans, adjacent to steep mountain slopes, and within the entrenched channels. The alluvial fans have been neotectonically deformed, faulted and their surface warped by small thrust faults that propagate from the mountain fronts into their forelands. Localised uplift rates are in the order of 0.1 to 1 m Ka(-1). (C) 1997 John Wiley & Sons, Ltd.