THEME : GEOLOGY
SATELLITE: Sentinel-2 L2A
INDEX: True color
IMAGES:
SUBJECT ANALYTICALLY:
This optimized True color script uses the visible
light bands red, green and blue in the corresponding red, green and blue color
channels, resulting in a product with natural colours that represents the Earth
as humans would naturally see it. The visualisation uses highlight compression
and improves the contrast and color vividness through minor contrast and
saturation enhancement.
Comments-observations
The two satellite images present the geomorphology of
Thassos, with the left one coming from 2016 and the right one from 2024.
Observing the images, a notable difference in the vegetation and general color
rendering of the island is discernible. In 2016, the image displays more
intense brown and dry shades, especially in the southern and western areas,
which may indicate past fires or reduced vegetation. In contrast, the 2024
image displays more green shades, which indicates a possible regeneration of the
flora or different climatic conditions that favored vegetation. Furthermore,
the coastal zones appear to maintain a stable morphology, with no apparent
changes in their geographical extent. Overall, the comparison suggests
environmental changes related either to natural processes or to human
interventions.
IMAGES:
A false color composite uses at least one non-visible
wavelength to image Earth. The false color composite using near infrared, red
and green bands is very popular (a band is a region of the electromagnetic
spectrum; a satellite sensor can image Earth in different bands). The false
colour composite is most commonly used to assess plant density and health,
since plants reflect near infrared and green light, while they absorb red.
Cities and exposed ground are grey or tan, and water appears blue or black.
Comments-observations:
Observing the images, a difference in the distribution
and intensity of vegetation is discernible. In the 2024 image, the red areas
appear more extensive and uniform, while in 2016 darker zones are observed,
possibly indicating vegetation loss due to fires, drought or human
interventions. Also of interest is the existence of areas with lower infrared
reflectance, which may be related to damaged or regenerating vegetation. The
comparison of the two images shows the dynamic change of the natural
environment of Thassos, highlighting the importance of satellite observation
for the management and protection of ecosystems.
INDEX: Geology 12,8,2
IMAGES:
SUBJECT ANALYTICALLY:
This
composite uses short-wave infrared (SWIR) band 12 to differentiate among
different rock types (a band is a region of the electromagnetic spectrum; a
satellite sensor can image Earth in different bands). Each rock and mineral
type reflects short-wave infrared light differently, making it possible to map
out geology by comparing reflected SWIR light. Near infrared (NIR) band 8
highlights vegetation and band 2 detects moisture, both contributing to
differentiation of ground materials. The composite is useful for finding
geological formations and features (e.g. faults, fractures), lithology (e.g.
granite, basalt, etc.) and mining applications.
Comments-observations:
Satellite images of Thassos, taken in 2016 (left) and
2024 (right) using the Geology 12,8,2 index, highlight changes in the
geological and soil composition of the island. Looking at the images,
differences in shades can be seen, with the 2016 image showing more intense
brown and red areas, especially in the southern and western areas, which may
indicate bare soil or exposed rocks. In the 2024 image, the presence of more
uniform green tones may indicate either changes in vegetation or natural
changes due to erosion or human activities. Also, the appearance of light
clouds in the right image may affect certain geological features.
INDEX: Geology 8,11,12
IMAGES:
SUBJECT ANALYTICALLY:
This
composite uses both short-wave infrared (SWIR) bands 11 and 12 to differentiate
among different rock types (a band is a region of the electromagnetic spectrum;
a satellite sensor can image Earth in different bands). Each rock and mineral
type reflects shortwave infrared light differently, making it possible to map
out geology by comparing reflected SWIR light. Near Infrared (NIR) band 8
highlights vegetation, contributing to differentiation of ground materials.
Vegetation in the composite appears red. The composite is useful for
differentiating vegetation, and land especially geologic features that can be
useful for mining and mineral exploration.
Comments-observations:
From
the comparison of the two satellite images of Thassos (2016 left, 2024 right),
significant geological variations are observed. The color changes indicate
variations in the composition of the rocks and possible geomorphological
changes. Specifically, it appears that certain areas, mainly in the southern
and central parts of the island, have shown strong changes in the relief,
possibly due to erosion or human intervention. In addition, variations in the
infrared bands may indicate changes in the vegetation or in the geochemical
composition of the rocks.
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