Geology
Nepal's Himalaya are the result of the Indian plate ramming northwards with particular force into Asian plate.
It has been estimated that a 2000-km cross-section of land along the collision zone has been compressed into 1000 km, doubling the thickness of the crust and producing not only the Himalaya but also the vast Tibetan Plateau.
The movement of plate increased the bed of Tethys Sea that covered the entire region. It eventually disappeared leaving evidences of sedimentary deposits and fossils such as ammonites . Kali Gandaki River formed a deepest gorge in the world, between Annapurna and Dhaulagiri both measuring above 8000 m.

Most of Nepal's present features were created at the geological last minute. Beginning 500,000 years ago, the Tibetan rim lunged forward along numerous fronts to form modern Himalaya. Averaging 8000 m, the Nepal's Himal (massif) show a freeze frame of state of play.
But mountain building produces downs as well as upon: around 200,000 years ago a foothills subsides, creating Nepal's Midland Valleys, while the southern edge of this pushed up to form the Mahabharat Lek and still further south the Chure Hills (called the Siwaliks in India). These ridges rose so rapidly that they forced many rivers to make east west detours and permitted to form three principle basin namely Koshi, Narayani and Karnali and their outlets to the Terai; Bagmati River were initially dammed up by the Mahabharat Lek, flooding Kathmandu Valley.

Nepal's' valleys are like vast cutaway diagrams of geological history, and trekking or reading them you'll be able to imagine the forces that have shaped the Himalaya. Igneous intrusive rocks (usually granite) are common, but most outcrops consists of metamorphic rocks (schist's, limestone's and dolomite), deposited as underwater sediments and later mashed and compacted under tremendous pressure; wavy light and dark bands of the Lhotse - Nuptse wall of the Everest Region contain fossilized ammonites (spiral shaped mollusks) dating from million years ago. Of a much recent origin, the bones of Peking man and primitive tools have been found in Chure Hills - proving that the Himalaya are so young that human were present during their creation.

Amphibians and reptiles
Terai is a main place of many cold-blooded animals. Marsh Crocodile inhabits rivers and lakes of terai and feed upon any animals that it can hold on to by strong jaws and also prefers scavenging. The more endangered Gharial crocodile with a long snout, measuring close to 7 meters is a selective one that prefers the flowing water and fish only. (Their main residents are Narayani, Rapti and Karnali River).

Frogs are worshipped by many ethnic communities as the crop protectors.
Nepal has surprisingly large diversity of poisonous and non-poisonous snakes. They are active during summer season. The biggest of the sub-continent include Indian Rock Python that may grow close to 10 meters in length. King Cobra the biggest poisonous snake is rare and found in Chitwan.
The other non-poisonous includes the rat, cat, tree, garter, sand boa and worm snakes. Poisonous include the common cobra, Pit vipers, vipers, and craits.

Birds
Nepal supports over 10% of the world’s bird species diversity. Kali Gandaki Valley lies in the cross road of bird distribution. It is the culminating point for the distribution of Eastern species such as blood pheasant and western species e.g. Cheer pheasant. Pokhara valley and the surrounding is where all the eight vulture species occurring in Nepal are found. There are transcontinental and altitudinal migration of birds in Nepal.

Lammergeier’s wing span measure over 3 meters. The tallest includes the Sarus Crane measuring close to two meter tall. The smallest include the Tickell’s Flowerpecker that measure just about the size of the thumb. The specialized feeding habit of birds include the piscivorous, nectarines, bone marrow eaters, filter feeders, seed eaters and carnivores,
Spiny Babbler is the only endemic species recorded for Nepal.

The colorful Danfe (Lophophorus impejanus) have been declared as the national bird.
The famous wintering area for the wetland birds are Koshi Tappu, Chitwan and Karnali. Beeshazar, Jagadishpur and Ghodaghodi Lakes are the newly listed Ramsar Sites that provide wintering site for duck and other waders. There are about 150 winter migrants residing in forest and wetlands.
The famous bird watching sites of Nepal are Shivapuri and Phulchowki hills surrounding Kathmandu, Pokhara and Modi Valley of Annapurna Sanctuary, Langtang Valley, Arun Basin, Royal Chitwan National Park, Bardia, Shukla and the wetlands of Koshi Tappu, and Jomsom.

Mammals
Nepal has a large diversity of flora and fauna including a considerable number of mammal species. This diversity is explained by the country’s diverse topography, wide range of altitudinal and bioclimatic zone together with the fact that lies at the point of Indo – Malayan and Palaearctic bio-geographical realms. The Himalayan region is also termed as zone of penetration and limitation by some authors.

A total of 181 mammals species have been recorded from Nepal belonging to 39 families of 12 orders. The major mammals represented in Nepal are Rodentia (43 spp), Carnivora (42 spp), Chiroptera (bats with 37 spp.), Artiodactyla (even toed ungulates with 22 spp.), and Insectivores (15 species) and Lagomorpha (hares and pikas with 10 spp).
One rodent species (Apodemus gurkha ) is endemic to Nepal. It occurs in Central Nepal between 2200 m to 3600m. Its habitat is mainly in conifer forest where it is marginally sympatric and syntropic with Wood Mouse (Apodemus sylvaticus).Pygmy Hog (Sus sylvanius) and Indian Chevrotian (Moschiola memonna) have been extirpated from Southern belt of Terai. Their record of occurring in Nepal awaits corroboration. The highest diversity of mammals species occur in midhills. However larger and the endangered species occur in the Terai and Siwaliks.

Observation of wildlife is easier in Terai as compared to mountains. Annapurna Sanctuary and Everest region is good for viewing mountain mammals.
Twenty seven mammals have been given legal protection by NPWC Act 1973. The big five (rhino, elephant, Bengal tiger, snow leopard and musk deer) drew attention from conservationist due to the vulnerability from the habitat fragmentation and casualty by poachers.
The Asian one-horned Rhino (Gaida in Nepali) is one of the five species of Rhino found in Asia and Africa. They are endangered and occur in Royal Chitwan National Park. They have been reintroduced to Bardia and few to Shukalphanta. They graze singly or in small group in elephant grass, where they also retire during the heat of the day.

Fish
One hundred and eighty five species of fish belonging to 11 orders have been recorded from Nepal. Eight endemic fish species are found in Nepal. Small populations of an exotic species Rato Macha (Carrasius carrasius) have become naturalized in the ponds of Nepal. The number of fish species found in river systems is related to the temperature and the rate of flow. The warmer the climate and the gentler the flow, the higher the number of fish species. All the 11 orders of fish reported from Nepal are found in Terai and Siwaliks, eight in the Midhills and only one in the highlands (Appendix4-7). The highest number of fish species – 154 species (83%) are found in the Terai/Siwaliks followed by 76 (41%) of the species in the Midhills and only six (3%) of the species of fish have been recorded in the Highlands (Table 4-7 and Figure 4-1). The low number of fish occurring at high altitudes is due to the prevalent adverse ecological conditions such as steep gradient of the streams and the cold temperatures.

Butterflies
In Nepal, there are excellent representation of butterflies found both in Oriental and Palaearctic realms. The total diversity of butterfly reported so far comprises about 650 species out of 20000 species found in the world. All these species are categorized under 11 families of the existing 15 families in the world. About 29 species and subspecies have been found endemic to the country.
Butterflies have been found thriving at the maximum altitudinal level of 5500 meter in the Himalayas. Parnassius acdestis (Sikkim Banded Apollo), Aglais ladakensis (Ladak Tortoise Shell) and Pontia sherpae (Sherpa White) exist in such high level of altitude in the West Himalayas. Parnassius species (Apollo) are confined above 2700 meter of elevation stretching from east to the west Himalayas. Speciation has been found high among the Himalayan species.
Mid mountain region is the meeting point both for the Palaearctic and oriental species. Among the notable and rare species found in this part include Teinopalpus imperialis (Kaiser-E –Hind), Papilio krishna (Krishna Peacock) and many other interesting species.

In Kathmandu:
The valley floor of Kathmandu and it’s surrounding mountains remarkable and display more than 360 species of butterflies of different status level. Teinopalpus imperialis, Papilio krishna, Diagora nicevillei, Troides aeacus etc. are the notable species found in Kathmandu. The southern part stretching from Godavari to the Phulchowki can be considered to be one of the most potential sites for the butterflies of Nepal.
Shivapuri National Park is the next hot spot for the diversity of the butterflies concerned. Studies carried out in different periods revealed the existence of 102 species of butterflies in this Park. Rare species like Papilio krishna has been reported at an elevation of 2120 meter of Shivapuri Mountain.
There are also endangered species in Godavari and Nagurjun forest.