Water, Life and Geology
Authors: freyssinel ines 
Published: March 2020

&lt;p&gt;In Geology, water plays a major role in the transformation of landscapes. Hot water springs can be exploited as geothermic resources. The first forms of life on Earth, cyanobacteria, lived in water. I studied these three examples with my students, implementing various educational strategies: field trips, academic conferences, and hands-on activities.&lt;/p&gt;&lt;p&gt;Example 1-Fields trips&lt;br&gt;In Marseille, I organised a geological outing in the Calanques, the protected rocky coves, which explains the geological history of the region as well and erosion and sedimentation phenomena. The Calanques are made of limestone rocks that were formed by the accumulation of marine organism skeletons at the bottom of a warm sea during the Secondary Era. During the Cretaceous period, the calcareous rocks were pushed to the surface through the tectonic trust and overlapping of the African and European plates. The topography formed (The Provencal and Pyrenean chain and its foothills) undergoes weathering, fractures and distorts under the action of water. The hot rainy periods allow chemical dissolution and facilitates the formation of karstic networks. The periods of glaciation during the quaternary provoke declining water levels and sculpted furthermore the ground thanks to glacial action. &lt;br&gt;&lt;br&gt;In Eastern Africa, in Djibouti, exceptional field trips were possible with the students&amp;#160; to the sites of the Assal-Goubbhet lake. It is a place like no other, a large depression 150 meters under the sea level.We studied the specific hydrological exchanges which explain the water hypersalinization. We measured the elevated thermal flows of the hot-water springs and linked our findings to tectonic activity. &lt;br&gt;&lt;br&gt;Example 2 - Lab activity with stromatolites.&lt;/p&gt;&lt;p&gt;Water and the first Life forms.The 3.5 billion year stromatolites are bio-constructed and sedimentary rocks. They bear witness to the presence of life forms in the oceans, cyanobacteria. An exploration of the terrain and a practical session enabled the students to discover the action of these living organisms on the primal atmosphere and grasp the concept of Actualism in Geology. &lt;br&gt;&lt;br&gt;Example 3 - Conference, field trip, and practical activities on geothermal activity.&lt;/p&gt;&lt;p&gt;Djibouti aims to become self-sufficient in energy by 2035 thanks to the production of 100% renewable electricity. The country relies on geothermal energy to reach that goal. We therefore studied this theme with the students of the French Highschool. Outings permitted to photograph the hot springs. Rain water infiltrates the ground and heats when in contact with the magma chambers less than 4 km under our feet. Through rock crack cause by earthquakes, the water comes to the surface in the form of steam and concentrates in the hot springs.&lt;/p&gt;&lt;p&gt;These examples remind our students of the essential role of water on our planet and its unequal distribution as a source of life, as a factor in the transformation of the landscapes or as a vital energy source. &lt;br&gt;&lt;br&gt;&lt;/p&gt;