Simulatión of crystallization on the Mediterranean sea floor in the Messinian:

Introduction

A crystal is characterized by a highly ordered internal structure, which manifests itself externally in flat and well-defined faces [1]. This internal order is the result of a repetitive arrangement of atoms, ions or molecules.

Approximately 5 million years ago, the Mediterranean Sea experienced a drastic reduction in its level, an event known as the Messinian Crisis [2]. During this period, large thicknesses of salts were deposited on the sea floor, the result of the evaporation of water and the subsequent crystallization of dissolved minerals (carbonates, gypsum and soluble salts).

It is well known that a practical method to obtain crystals in the laboratory is through the drying of a brine [3, 4]. In this work, an experimental activity is proposed to simulate, on a laboratory scale, the conditions that led to the formation of these saline deposits present in the Mediterranean Sea. Through this practice, high school students will be able to understandthe principles of crystallization and the methods of crystal synthesis in a deeper way, some of which are evaporation crystallization, crystallization from a solution and gel crystallization [4]. In addition, the relevance of crystallization in large-scale geological processes will be studied.

Objectives

· To understand the process of crystallization in nature

· To simulate and learn about extreme sedimentary environments

Secondary objectives

· To practice obtaining pure substances in solution.

· To separate substances in the form of crystals

· To prepare students for undergraduate studies

Materials and methods

Materials: oven, stove, hot plate, microscope, binocular magnifying glass, precision balance, stirrer, beakers, crystallizers, watch glass, glass rods, thermometers, mortars, bunsen burners, distilled water, calcium carbonate, calcium sulfate, anhydrite, common salt, Himalayan salt, magnesium, iron, potassium and gels.

Methods: Use of different techniques to crystallize substances soluble and insoluble in water: Crystallization by evaporation, crystallization from a solution and gel crystallization [5]. To carry out the crystallizations, the following procedure is generally followed: Preparation of the solution: the desired amount of substance is weighed on a scale based on its solubility, and is added together with the necessary volume of water to a container to heat the mixture with intermittent stirring.

Conclusion

By using different crystallisation techniques, materials and working conditions, different substances will be created and they will reflect the deposits that originated in the Mediterranean Sea 5 million years ago. In addition, the influence of certain factors such as the density of the nuclei, the degree of supersaturation, the presence of impurities, the available space or the cooling speed on the shape and size of the crystal will be studied.

Likewise, through the study of the most relevant evaporite rocks of Andalusia, with special mention to the Pulpí Geode in Almería and the gypsum of Sorbas, their economic importance will be revealed.

Bibliografía

[1] Amorós, J.L. (1982).

[2] Krinjgsman, Wout, et al.

[3] Burillo, María José Mayayo; OLIETE, Alfonso Yuste.

[4] Benavente García, D. et al; Enseñ. Cienc. Tierra 2018,

[5] Aguado Bernal, Rafael, et al. 2013.