Serpentine, recently discovered on Mars using Mars Reconnaissance Orbiter data, is uncommon but found in three geologic settings: (1) in melange terrains at the Claritas Rise and the Nili Fossae, (2) associated with a few southern highlands impact craters, and (3) associated with a regional olivine-rich stratigraphic unit near the Isidis basin. Any presently active serpentinization processes would be occurring beneath the surface and mineral products would not be apparent with surface and orbital data; however, finding serpentine in several Noachian terrains indicates active serpentinization processes in Mars' past. Important implications are the past production of magnetite, which may contribute to chemical remnant magnetization of Mars' crust, and production of H_2, which is a suitable energy source for chemosynthetic microbial life.

Geologic Setting of Serpentine Deposits on Mars

Role of effective discharge on morphological changes for a regulated macrochannel river system

Large dams impose an artificial flow-sediment regime that affects the alteration along channel form and riverine habitats. The present article synthesizes the knowledge on growth of large dams in I...

Regulated rivers in India: research progress and future directions

Detecting and quantifying hydromorphology changes in a chilean river after 50 years of dam operation

The anthropogenic activities affect the river channel as well as the whole system in different magnitudes and dimensions. Barakar River, the main tributary to the Damodar River in eastern India, is modified by several engineering structures. Hydrological parameters, such as monthly discharge, peak flow discharge and geomorphological factors, such as gradient, width–depth ratio, grain size, braid–channel ratio, sinuosity ratio, riffle-pool sequence, and stream power are taken into consideration to highlight the significant alterations of the river due to dam and bridge construction. The alterations are assessed with the help of hydrological data, satellite images, and digital elevation data along with field survey. The downstream section of the dams, the river is characterised by high braiding, sinuous, total and unit stream power along with the presence of a box-shaped bedrock channel, high gradient, bed coarsening and armouring due to the release of high-velocity sediment-free ‘hungry water’. In the upstream reach, the grain size decreases towards the dam, and it increases suddenly with poor sorting at the immediate downstream regime of the dam. The effects of bridges on the Barakar river morphology include an increase of gradient, width and depth of the river channel at the downstream of the bridges. The construction of bridges influences riffle-pool sequences. Thereby, the pool depth spacing is greater than the riffle crest spacing. However, the integration of natural as well as human-induced factors can be the best approach to understand the anthropogenic alteration of the river. Moreover, construction of some check dams at the upper section of the tributaries of the Barakar River can be very effective for morphological stability.

Changes in the hydrological regime and channel morphology as the effects of dams and bridges in the Barakar River, India

Rivers play a significant role for sustainment and development of human race. The number of river interventions is increasing to meet water and energy demand. The present paper discusses impacts of...

Impact of river interventions on alluvial channel morphology

River interventions disturb the natural flow regime of channel. The impacts generated from river interventions is categorized based on the alteration of fluvial system including channel planform and ecology. The Brahmani River, one of the major peninsular river holds a significant importance for three major states of eastern India. This river has been subjected to periodic flooding events damaging high value property. Rengali multi-purpose river valley project (since 1985), located along middle reach of Brahmani, influence the downstream stretch behavior. A planform variation of increased braiding pattern is observed for downstream river. Interaction of reservoir-catchment along with planform variation assessment embraces a substantial importance for geologists and engineers. This research article aims to quantify variation in channel planform for pre-Rengali and post-Rengali time period along a selected reach integrating Sinuosity Index (SI) and Braid-Channel Ratio (BR) parameters using remote sensing techniques.

Chandan Pradhan

Papers

Impact of river interventions on alluvial channel morphology

Role of effective discharge on morphological changes for a regulated macrochannel river system

Regulated rivers in India: research progress and future directions

Assessment of post-impoundment geomorphic variations along Brahmani River using remote sensing

A geomorphic approach to evaluate river recovery potential for regulated river basin